If a tank loses aggro, whose fault is it?

[ShaneDawn]

Most of the blame imho goes to dps, because dps can stop when aggro warning lights on, but he doesn't care. Insufficient tank may slow down dps for this, but dps can avoid get aggro in every situation.

If the tank is bad, the blame is on DPS?

Tbh there are only so many cases where DPS is actually responsible for pulling aggro:
1.) The tank is severely undergeared in comparison to the DPS
2.) The DPS prepull mobs before tank has a chance to pick them up
3.) Not using their aggro mitigators, Quelling Strike, Shadewalker, Smokebomb, Elusive Jump etc.
4.) Any and all combinations of the above.

The DPS is in no way responsible to slow down DPS, if the tank is doing something blatantly wrong. Should you slow down? Maybe. Is it your fault if the tank is not doing a half decent job? Absolutely not.

[LalaRu]

If the tank is bad, the blame is on DPS?

Nope, bad tank is bad, you can't do anything on it, I were just referring to the pull of hate, that dps can avoid, but it can happen at higher price, see below.

Is it your fault if the tank is not doing a half decent job? Absolutely not.

Sure thing, and I agree. We were just talking about pull aggro, and as dps I can really avoid it, to the extent I can just stop dps and dance manderville until the flag goes yellow again. But after all we want complete a duty, and depending where we are, I am willing to take aggro and kill the mob for sake to get out there sooner o later. Sooner is better.