Quick list of pretty basic stuff that DPS never seems to notice but probably should. If you can get your guys to keep an eye out for this stuff, your life will get a lot easier.
- Knockback/knockup: If at any point the tank goes flying through the air, you need to slow your dps. Knock backs very often come with a threat reduction. Knock ups usually don’t but usually isn’t always. At the very least, the tank isn’t generating any threat while running back to a mob.
- Roots/snares: Usually if a mob is able to root the tank, it will do so and then run away and hit the tank from range. While the tank is rooted, he is generating zero threat. If you are able to dispel the root, don’t hesitate, just do it. If a mob has a snare or slow on the tank, realize that if you pull aggro or if the tank gets knocked away or is in some other way far from the mob, the tank is going to take a long time to get there and start generating threat again.
- Stuns: These are the tank killers. When a tank is stunned he loses all of his avoidance and can find himself dead rather quickly in some situations. If you can cleanse the stun, do it. If you are a healer, step up the heals. If you are a dps, you need to be aware that a stunned tank generates no threat. This is particularly dangerous when a tank gets stunned at the very beginning of a pull. There are a lot of mobs in TK that get stun happy
- Debuffs: If a mob puts a debuff like a damage reduction or attack speed slowing, dps has to realize it and know that threat is going to be lower (Tidewalker or the leviathons in BT come to mind).
- Casters: If a mob has a lot of Random Secondary Targetting spells, then all that time spent casting is time spent not hitting the tank so the tank will probably be short on rage. There are some robots in TK that are particularly bad about this and iirc they also have a knockback.
- Charge: Sometimes mobs with a charge will drop aggro when they charge so stopping dps is a good idea (think Doomwalker or the ogres in Gruul’s Lair). Even if they don’t drop aggro, realize that the tank is generating zero threat while the mob is running back to him.
- Mind Control: Mind controlling mobs usually do not target the person who has the most threat. Keep in mind that most threat is not necessarily the same as the person with aggro so dps needs to stay below tank’s threat, not just below aggro gain. If the tank gets MCed, dps should stop so that the tank can easily regain the mobs. MC is usually not a threat wipe so if DPS stops, the tank can do a shout as soon as the MC ends and the mobs should goback to him. I always advocate killing MCed players, but that is probably a bad idea when it’s the tank. Also, if the tank wants to get in on the fun (I usually do) of killing the MCed player, he isn’t going to be generating any threat on the mob so you might as well hold off on dps and help kill the guy who got MCed.
- Aggro wipes: This is almost always a boss thing, I can’t think of any trash mobs that just plain wipe their threat list (except for a few that do it when they charge). This is one where it is the tanks responsibility to pick up the mob just as much as it is the DPSers responsibility to lay of for a few seconds. Hydross, Leotheras, Doomwalker, and Illidan are the ones I can think of who have mid-fight aggro wipes. A good tank won’t have trouble picking the boss up as long as dps restrains themselves. These are usually pretty easy to deal with since it is generally a major mechanic of the fight so its not going to catch anyone by surprise.
- Fear/Reflect/Interrupt: There are some cases where the tank needs to keep his global cooldown clear so that he can interrupt a heal or some other important spell or so that he can break a fear. During that time the tank is doing nothing for threat but heroic strike. Likewise, if there is a something that the tank must reflect, he will just be sitting there waiting for it to be 100% sure he has enough rage to get the reflect off. (Spell Reflect should be effected by Focused Rage IMO but that is a whole other discussion). Like aggro wipes, this is mostly a boss only type of thing and is generally a major mechanic so people tend to be conscious of it.
That’s all I can think of off the top of my head. Feel free to add a comment with anything I missed. The idea is that this is pretty basic stuff that DPSers can and should be aware of instead of mindlessly smashing their fireball button.