Pet aggro bug?
 

A player on my server, 52 magician, was using his best earth pet today. His pet would do a fair amount of damage before the mage would start nuking mobs. After doing the smallest amount of aggro/damage, the mob attacks the mage. I've read aggro lists. At over 1000 points of damage done, the earth pet has generated only maybe 100-150 aggro, while a simple spell from the mage will generate somewhere over 300. Compared to other pets/classes, it looks like the pet is doing 10% of the aggro it should be generating.

All this happened all of a sudden. No changes happened to my server. And the mage has been grinding exp at the same location for days. Any advice about what to start looking for next?

well check the rules table for spells and pets agro, just in case