It's extra bad in TB and in the Molten Front. xD It happens a lot when doing dailies on Cam, though. Not sure about my hunter's pet as my hunter is a scrub and I can't take on that many on-level mobs with her anyway. When several mobs (like 4+) are meleeing my toon or Cammie's pet.
When any elemental is meleeing my toon. On some heroic encounters, such as the first boss of Tol'vir, the mechanical boss in Deadmines, the larger pulls in Stonecore, and on many pulls in Vortex Pinnacle. It happens most often in the Atramedes encounter, and occasionally when Ignacious charges in my general direction. I try to anticipate it but I can't always. When Cho'gall targets where I'm standing with the crash thing, I usually lag. When Valiona & Theralion target me with special abilities I lag for a sec, which is why I don't always move immediately.
Occasionally on boss encounters that require the boss to target or charge my toon.
When I use a pet to tank, and when that pet uses a taunting spell. When I'm on a toon that can't even tank, but grab aggro as if I were tanking (such as, the actual tank dies and I want the healer to live so I use something DPS-ey that causes lots of threat and pray). When I am not in tank spec, but use bear form, righteous fury, blood presence or defensive stance. When I DPS or heal, all is normal, but as soon as I start tanking, I get MAJOR lag spikes.
