The Dryad "Summoner Playstyle" sphere says it will increase DPS for your towers by 15% when the Dryad is not corrupt. It does increase the DPS by 15% when inspecting the tower, but the buff does not seem to deactivate when you change to the corrupted form. It also stays active when you switch to different characters completely, though I am not sure if it should in that case
The second case is working as intended. The first case, it appears that the DPS doesn't visually drop when you go corrupt, but the damage it deals IS reduced. You can see this on the dummy. I'll approve this for the sake of the visual DPS being incorrect.