I wouldn't say it's a "terrible way to use it". If anything it's far too convenient, since it's a "fire and forget" you have to activate once and never disable again.
More than anything is a wrong implementation, since UD is supposed to be a REACTION that consume your... well, reaction, and can be activated just once per round, rather than being a passive with no downside whatsoever.
Agreed, but I would also do this with the OP saying that it's presented in unintuitive manner. I would almost end the game without realizing it's here and wondering where is that reaction my two rogues should have, but then that's maybe on me as I'm a person who knows D&D rules and I expected it to be a reaction. ^^"
