Listening to the rock is a good thing, especially as it applies to Wow. The best thing for groups is if everyone knows their role, does it, and doesnt whine about the other roles in the party.
I've always gravitated towards the Tank or Healer roles in Wow (Big surprise, my first character was a paladin). If I'm tanking, I'm doing my best to make sure as many of the baddies as I can manage are beating on me and not the DPS or healers with their soft outsides and rich creamy centers (that must be why mobs go after them unless they're gently "persuaded" to do otherwise, right?). I expect the healer to keep me healed enough to do my job. Enough, not all the way full. If I end a fight with 1hp and everyone is still standing, its successful.
As a healer, it is both more and less complicated at the same time. It's almost like an instant exercise in triage, who needs healing the most, for the best benefit of the group. Sorry for you DPS, you're probably not it. Most good players know this. Don't worry, I'll rez you after we've won. Most tanks I know hold aggro fairly well, I have seen PUGs where this is not the case, but those don't last too long. If you pull aggro and die, you probably had a hand in it.
I will be honest, I have only a handful of times been DPS in a group. This is limited to fury warrior and a few times each warlock and mage. However, a few things should be clear. Crowd control is part of the job. Sheep, charm, sap, trap, take your pick, you probably have CC abilities. Another thing that should be clear is that if you do too much damage too quickly, you will pull aggro. This will most likely result in injury and/or death.
I am not trying to say any one role is more valuable than the others. Unless you can solo the instance, you require support, thats why we group in the first place. I will be the first to admit quality CC is worth it's weight in gold. Tank has less to worry about, there is not as much damage taken, everything is smooth. What I'm saying is next time you run an instance, think of what the Rock would say: "know your role and shut your mouth!"
Mid Afternoon Quickie
9 months ago