Aggro generation has been an issue since imbues were introduced. I run an archer with 31 sneak attack dice and 15 imbue dice, and in R1 raids with 45% threat reduction I constantly pull aggro just by autoattacking. It's become a running joke in my guild when I pull aggro and the boss kills me. It's not a tank issue either -- it happens with different tanks. I'm not the only one in my guild with this problem. Other optimized ranged characters, especially those with a heavy imbue focus, pull aggro off the tank constantly.
One of the fundamental problems with threat generation is that Diversion items only affect the front number of an attack. It does not affect sneak attack, imbues, and other weapon procs. The other fundamental issue is that tank hate generation (ie, Intimidate) does not scale based on difficulty. It's much easier for tanks to grab and maintain aggro in high skull reaper than it is on Legendary Hard.
