Spells such as Emotion:Hopelessness are fantastic - when they work. In that the problem really lies, as getting the enemy to fail it's saves/MR can often be the real reason people don't bother to use them too often in BG. There's one area in IWD where these babies come at you thick and fast. The results for the unprepared party are somewhat obvious.
Confusion does give a -2 penalty to save, and Chaos has a -4 for those
over 5th level. So, yes in answer to your question, such spells can be lethal if used correctly and they work. The same could be said about a good many others too. If it wasn't for the save I'd use Chromatic Orb. As it is, I find it's presence insulting if it takes up the space of an (in-)valuable Magic Missile. Others feel different of course.