The only time when a tank should be losing mobs at all is in large gear level difference situations or if a group is large and somebody goes balls to the wall on the straggler mob that always takes 8 minutes to make it to the group. Tank stance in this game gives obscene hate potential and honestly the hate increase on the moves themselves give enough that most of the time there shouldn't be an issue in DPS stance outside of group pulls.

I don't care how good you think your DPS is, if a tank knows what they are doing and uses all their tools at their disposal then hate should be a non-issue.

Now if DPS are purposely doing things to hamstring your pulls and make it more difficult to gather mobs then that is a whole 'nother basket of kittens.