I was making a post about dps,threat and other things... but I already read 7 of those today...
So here's the TL;DR version:
A DPS should never over-aggro the tank.
Now, this doesn't really counts for raids anymore I guess (no experience there) as it used to be in TBC, but it does count towards heroics. You may end up with a just-dinged-80... don't leave group, the run may take 5 minutes longer, just manage your threat.
There are also a lot of posts about CC today. Anyone remember that? It means Continuous Consecration... :p, just kidding, crowd control. It has no place anymore, except for a few pulls with casters in FoS and the waves in HoR. There are a lot of people who find that a shame, me included. But everything is an AoE-fest these days... why do we even have those spells??