File isn't clean, has extra cells, barnacles, and a crate dirtied. See https://www.tamriel-rebuilt.org/content/tutorial-tesame-tutorial for details
Cliffs are all steep, stretched terrain. They need to be covered with cliff/mt statics or made less steep.
Most statics are missing vertex shading underneath
Lots of objects hidden behind the cliffs/beneath terrain that need to be removed
Lots of texture seams on the terrain, when 3 textures touch you need to cover the square edges that appear. 
Some areas that are still completely flat that need to be raised or lowered  a little
Roads are mostly sunk well enough but the terrain is still rough and spikey and should be smoothed
That goes for most of the terrain, lots  of rough areas that need smoothing
BC grass statics shouldn't be resting on one point, sink them into the terrain a little bit
I don't understand why there are bone rocks in the south
I would recommend creating a 4-6 cell island instead of trying to work with the heightmap for your first area

I took another look, I think you should create an island from scratch. It looks like the only point you really addressed was the lack of objects covering the stretched cliffs. A lot of the terrain appears to still be in the default shape of the height map, and an important part of exterior showcases is to show your ability to shape the land yourself. It's important to take your time, and feel free to ask questions on discord. As for starting over, don't feel bad about it, I didn't submit my showcase until my 4th island.

-Take another look at almost your entire coast line, you will notice lots of jagged and spiky bits that need to be smoothed. An easy way to check for terrain that needs to be smoothed is to cycle between wireframe (W) and regular view. In certain cases where smoothing will do too much damage and ruin terrain shapes you can carefully move spikes with 1 radius landscape editing in wireframe (W) mode.
-Your road is mostly not sunk, and in places where it is you have jagged terrain. Take a walk in game from seyda neen to balmora through the ascadian isles to see nicely sunk roads.
-When placing marshmarrow together make sure they lean in different directions so it doesn't look repetitive
-Some of your scum ponds have lily pads sunk beneath them, causing them to not appear
-Different BC mushroom species should be growing together instead of having entirely different clumps for different mushrooms, you should also make sure all mushroom patches have a BC mushroom light paired with them.
-Rocks forming in large clumps IS something that happens in the Bitter Coast so you were right to copy it here, just make sure to not get into the habit of it since it doesn't always look great.
-Make sure you're vertex shading under statics, some trees and rocks are missing shading underneath.
-In -8,-3 there is a T_Mw_TerrRockBC_RockGrp_02 which has the top rock caspering, which means it has the under side of the mesh that you can see through showing.
-The dock is full of floating and bleeding objects, you're going to want to take another look at all of the placements here.
-The dock is also not properly connected, you need to look at the poles to make sure they have an end and aren't caspering.
 

-You still need to smooth your jagged terrain, look closely in wireframe, you will see a lot of areas like this: https://i.imgur.com/Q7pwD5y.png + https://i.imgur.com/k0vDRc8.png + https://i.imgur.com/KnSMHei.png you will want to select this: https://i.imgur.com/TVHf6QR.png in your Landscape Edit window to smooth the patches, which will then look like this: https://i.imgur.com/FtVFnjq.png + https://i.imgur.com/1Pj2Wfu.png

-Your road was sunk better this time but now has the same jagged terrain problem as above.

-Marshmarrow rotation has been improved

-Lilypads have been fixed

-Mushrooms and mushroom lights have been fixed

-Vertex shading has improved

-The rock group I mentioned is still caspering: https://i.imgur.com/KOOY6SH.png

-The dock still has lots of floaters and bleeders: https://i.imgur.com/OY8tlrl.png + https://i.imgur.com/xSw3Um7.jpeg

-The dock still isn't properly using end pieces: https://i.imgur.com/dt7WwyX.jpeg + https://i.imgur.com/aZOLoXA.png

-You still need to smooth your jagged terrain, look closely in wireframe, you will see a lot of areas like this: https://i.imgur.com/Q7pwD5y.png + https://i.imgur.com/k0vDRc8.png + https://i.imgur.com/KnSMHei.png you will want to select this: https://i.imgur.com/TVHf6QR.png in your Landscape Edit window to smooth the patches, which will then look like this: https://i.imgur.com/FtVFnjq.png + https://i.imgur.com/1Pj2Wfu.png

The road is still jagged and needs smoothing

Rock group has been fixed

-The dock still has lots of floaters and bleeders

-The dock is now using proper end pieces, however you went and changed the stairs to a different set, which introduces the problem of set mixing. Docks should use dock steps, not cave steps

Don't be upset by the size of this, the fact that I was willing to do this detailed of a review means that you fixed most of the more obvious erros I pointed out in previous reviews and the actual review can start now. Speaking of starting now... 

Bitter Coast Region -9,-2
    Terrain needs smoothing on the hill south of ex_dwrv_ruin20 under water, and a blue water ref 256_ripple light should be placed by the kelp
        https://i.imgur.com/oJm1aFB.png
    Terrain needs terrain smoothing west of the sunken dwemer tower
        https://i.imgur.com/zPp6Vsq.jpeg
    Beach in the south of the cell needs terrain smoothing, and grey vertex shading where the water and land meet, a rock by the marshmarrow also needs shading.
        https://i.imgur.com/vfnui40.jpeg + https://i.imgur.com/KGlCMFR.jpeg
    The north hill could be smoothed more to have a nicer transition from hill to mud
        https://i.imgur.com/rfUUEDT.jpeg
    The beach by the entrance has a terrain spike that needs to be cleared, either smooth it or lower it carefully with 1 radius terrain editing. The hill above the entrance could use smoothing as well
        https://i.imgur.com/Gm3YUon.jpeg
    Both active_de_p_bed_28 on top of the hill are not resting on the ground nicely, and need to be rotated to be on the ground better
    Same goes for the dwemer chest
    furn_de_ex_stool_02 floating
    T_Dwe_DngRuin_F_BarrelOpen_01 floating
    The objects on the de_p table aren't resting properly, and the 2 dwemer coins are floating.
    Check this for detailed placement guidelines for de_p: https://drive.google.com/file/d/0Bxtf3PaWZqbXMlZPSnc3TGhfM0k/view?resour...
    dwemer_boots floating
    furn_crate_lid_01 floating
    2 crates outside the ruined wall floating, scrap wood and guar cart outside the ruined wall floating
        https://i.imgur.com/oUDZ8Bk.jpeg
    Terrain spikes along the road on the north island
        https://i.imgur.com/emOHps5.jpeg
    Texture seams on the hill, cover these with rocks or clear them by painting the same texture nearby
        https://i.imgur.com/d7NgNJq.jpeg
    
Bitter Coast Region -8,-2
    Beach and scum pond needs terrain smoothing and grey vertex shading where water meets land
        https://i.imgur.com/8nWti5t.jpeg
    Pit and mud beneath kelp patch need smoothing
        https://i.imgur.com/i9ImkrV.jpeg
    
Bitter Coast Region -9,-3
    2 spots on the west and south beach need smoothing, and the whole beach needs grey vertex shading where water meets land
        https://i.imgur.com/QEeGSJh.jpeg
    Texture seam in the north, by rocks
        https://i.imgur.com/7Nh0LZs.jpeg
    North of that, some bank needs smoothing, and the steep slope needs a bit of detail to hide stretched texture and jagged terrain. One or 2 medium sized rocks will fix this, you could also fix it by carefully editing it with 1 radius terrain editing, though this is not recommended for beginners
        https://i.imgur.com/dF0D8aq.jpeg
        
Bitter Coast Region -8,-3
    Tree needs more shading
        https://i.imgur.com/TlX6ldg.jpeg
    Whole beach needs grey vertex shading where land meets water, and a single small spot need terrain smoothing
        https://i.imgur.com/ay1wYhq.png
    Rock missing vertex shading
        https://i.imgur.com/CuxcFyC.jpeg
    Floating rocks on the north side of the cell
        https://i.imgur.com/U2XCld8.jpeg
    
Bitter Coast Region -7,-3
    Name your town, even if its just Stevetown
    Make your town Illegal to Sleep by going into the World menu, then selecting Exterior Cell. There will be a check box to tick
    There is a pathgrid, good job! Generally they don't have to have this many nodes, but its not a big deal and you should just use fewer next time.
    These docks can be hard to detail with their uneven planks, zoom in close underneath all of your crates and chests to check if there is a gap, some will need to be rotated a tiny bit to rest on both sides.
        https://i.imgur.com/R5FvfU9.png + https://i.imgur.com/sbM9p96.png + https://i.imgur.com/oZH3PbL.png
    In your rowboat there is a com_sack_02_thief bleeding very far. It's good to bleed sacks but less than this.
    Metal lantern hooks are too high class for a shack town, use ropes. Check out Hla Oad for an example
        https://i.imgur.com/msKNzJ7.png + https://i.imgur.com/xKDSVyP.png
    Don't set mix your docks, use dock steps instead of cavern steps
        https://i.imgur.com/8oFjF4U.png
    Look inside your dwemer barrels, they aren't rotated properly so they have terrain poking through the bottom.
        https://i.imgur.com/Omkys2c.png

Despite the size of this review, you're closer to completion than you think. Just fix all of this and we're good. Even if I missed something, don't worry about it, just fix these things I'm pointing out and I will promote you to exterior dev. I'm pretty sure I mentioned this before, but I'll say again since this is a more official review; I don't mind that you put levelled creatures and NPCs in your showcase, but generally that should be avoided when doing TR exterior claims.

Very good, a lot of errors are fixed and you are nearly done, but I need you to really pay close attention to the terrain. While this version is an improvement, there are areas where it's still not being fixed properly. After finding the jagged spots in wireframe (W) and smoothing, you still need to inspect that they are actually smoothed by looking in wireframe again. If you aren't sure, ask.

Bitter Coast Region -9,-2
    All floaters in dwemer ruin except for one plank are fixed
    Terrain still spikey and jagged by Dwemer entrance
    
Bitter Coast Region -8,-2
    Beach still needs terrain smoothing
    Beach vertex shading fixed
    
Bitter Coast Region -9,-3
    West beach still needs terrain smoothing
    River and beach of north island needs terrain smoothing
    Beach vertex shading fixed
    Hill detailed
    terrain_rock_bc_15 on the west of the island needs to be sunk or rotated more, faceless bottom of the rock is showing (known as caspering from here on out)
    
Bitter Coast Region -8,-3
    Beach terrain fixed
    Beach vertex shading fixed
    
Thistown -7,-3
    Dock placement errors fixed
    Lantern hooks fixed
    Illegal to sleep is set
    The steps are still a problem, you fixed the set mixing but then placed them in a way that doesn't work. Since there are no steps that fit this level difference we are going to have to find another way to connect these dock layers. Option 1 would be to remove the steps entirely and bring the lower dock UP to the other's level, or the upper dock DOWN to the lower's level, and have them connect normally. Option 2 would be remove the steps and place an ex_ship_plank.