Well, yes, IVs are kind of important. You don't want like 0 in each IV. However, say you're using a fast attacker that's really frail. Of course, I would ev train, as that's really useful, and make sure it has a good nature, however, you definitely want to have good IVs in its best attacking stat and speed. Bulk is nice, but if that thing is just a fast attacker, then its probably not going to take a hit with max IVs anyways.