Frankly, I would say it all depends upon the opportunity cost involved in obtaining those buffs or debuffs. For instance, would you be giving up damage or recharge, thereby drawing out the fight for longer, in order to get that bit of extra buff/debuff? If your character has access to a reliable self heal, could that make up the difference? Just how close to the razor's edge between survival and defeat does your character teeter on? I mean, if you can casually get like 17% defense on a resistance build, that's like knocking a third off incoming damage, but chasing 45% may hamstring your entire build...