I have had it happen while kiting nightmares, orcs, and shades in different places. Frequently the mobs will randomly warp away across the zone. If I my pet is attacking the mob when it warps it will warp to. The mobs in the new area kill my pet and the mob I was killing starts out of combat regen.
Would happen to me when kiting crocs -- I took off levitate and that fixed the issue. Mobs see you in the air, their z-axis pathing gets funky, and sends them off to the other side of the zone.
