It is relatively forgiving. But people doing it do need to know the mechanics, even if a few of them mess up occasionally.

For example, messing up might mean a bleed, a damage down, a bit more damage on party stacks, or a death+rez or Esuna. But if this happens to a lot of people, it's gonna slowly crumble the alliance away.

So provided you actually know the mechanics and mostly do them, if you just make a mistake here and there it's alright, but you can't really have the whole alliance in there being clueless (which is quite evident in blind prog parties).