The only problem i've found with this so far is that there are some tanks that will pull the 1st mob, move on to the 2nd mob and then stop for around 3-5 seconds (at which point I'm thinking "Okay, its go time") so I then cast regen on them. However at that exact moment the tank then starts running off in the direction of the 3rd mob and then I do a mental facepalm.