There does seem to be a bug with companions and aggro, because even when I use heavy attack on an enemy the companion runs to that enemy and immediately runs off to another. Instead of staying on the target I heavy attacked.
This is really noticable as when I get a marauder in the IA and there are still other enemies around, my companion totally ignores the marauder even though I did heavy attack him(multiple times). Which on Gothmau often results in dead for me.
This has been happening to me since the Gold Road update.
PS: Using Sharp with tank/taunt set-up!