It seems to me that rage control is a topic that is rarely discussed, if ever. Yet it's a game mechanic that exists, and in my opinion it is in need of a dramatic boost.
Rationale: with recent updates many sources of damage have been boosted. Since every point of damage enrages monster, their rage bar is now filling faster. In the meantime, as far as I can tell rage reduction abilities have not received the same boost, at least for most of them. In particular the recent AH change increased damage overall, but did not change the amount of rage reduction pets can apply (or if it did, it's not in the patch notes).
I tested the current state of rage control with Vidaria demons in the northern area, because many of their rage attacks are quite punishing and a control build is well-suited for them. Specifically it's Sword/AH, with Sword having all possible rage reduction mods you can have, and AH all possible rage reduction you can give to a pet. I am also using the level 78 Calligraphy recipe Obstinate+ to generate -18% rage.
The result in practice is that even if I focus on reducing rage as much as possible, never using any of the AH abilities that boost the pet's damage, I can barely keep up when fighting Justicars and Behemoths, and Overseers are just impossible to control (for some reason their rage goes up faster).
Note that if I was using Sic'Em I would activate rage reduction mods for the pet, but the additional damage mods I have for that ability more that counter this effect and the overall result is an increase of rage.
Granted, this is with a maxed out pet (Blinding Wasp), but still: I am not using AH offensive abilities. Except for the first attack, because I need the pet to get aggro quickly, the pet just uses its basic attack the entire fight.