As title says - the Hlaalu Guards in the eastern Andothren, on the eastern bank of the Thirr River, should wear the River Watch set.

Aside from the exterior guards, the guards in the following interiors also need to be changed:

Andothren, Barthel Moret: Clothier
Andothren, Docks: Port Authority
Andothren, Docks: Warehouse
Andothren, Eastern Guard Tower North
Andothren, Eastern Guard Tower South
Andothren, Felanius Civeran: Trader
Andothren, Hlaalu Council Manor (half of the guards, the rest should keep the Canyon Watch set)
Andothren, Irva Sedrethi: Outfitter