Gonna need your log neodite. But um I'm going to sleep, been up long enough for today, CodenameG should be on sometime, or another CC dev might happen to pass by and could take a look. GL man, but my mage was doing fine. They're really gonna need the log to do anything for it. Otherwise we just kinda go... "well it could have stopped anywhere."
EDIT: Your tank may also be somewhat of an idiot and is tab-targetting between mobs every .25 seconds, and IB is forcing you to switch to each of those targets, and the CC just can't keep up with targets that fast. So it sits there, and checks each one that comes up for Critical Mass, then Living Bomb, and by this time your tank has switched targets so your character follow suite. Just play by hand until a boss fight, then hit start. See what happens. You can also just watch, if you see your mage switching targets superfast it is the tank. And also IDK if CodenameG could put something in there to compensate for switching targets so much, but it would slow down the CC a lot.