I'm going to do some math to correct people who think you can't hold threat from a good DPS without tank stance, because they clearly haven't done the math. I'll use a DRK opener as an example since I have the numbers on hand here: https://docs.google.com/spreadsheets...DDw/edit#gid=0
With the following opener: Unmend (DA), Hard Slash (Carve and Split), Spinning Slash (DA), Power Slash.
The potency of the threat, with enmity modifiers is as follows: 150(x3), 150, 450, 220(x3), 300(x6.5) or a total of 1950 potency.
Divide that into potency of threat per GCD and you have 487.5, now add STR gear and there is no DPS job that can generate more threat than that. The only real threat is the off tank, in particular wars with deliverance openers. But in that case you may as well have them tanking and that would be the most efficient DPS wise.
I just did a test opener with actual damage on a dummy, since it's actual damage that determines threat.
648, 635 (1936), 908, 1354.
Add enmity modifers and you get the following: 1944, 635 (1936), 2724, 8801 for a total of 16040 threat in 4 GCDs. In order to overtake that the DPS has to be doing 2138DPS in the same time period (/7.5 assuming a 2.5 second GCD). So yes, you can pull without tank stance, I think the problem is that people don't realize how big the enmity boost is on your threat combos, your tank stance is only a part of your threat generation.
Also I forgot to add the potency given by using DA, or the fact that by pulling you usually have anywhere between half to a full GCD lead on the other jobs. Also I am not even full slaying, this is with i150 crafted.