Statslike games are full of this kind of "get X bonus, but it also sucks for reason Y". I guess the ostensible reason is Game Balance but actually you don't need the negative. The game will feel better, and players' thinking much more clear, if you just do the positive part.

@Jonathan_Blow Honestly, it depends on the context. Wording might be an issue - I'd use "deals 75% of based dmg" or nothing at all, since the dmg range is clearly displayed just below the level line.