In my opinion obsidian is trying to cure a symptom instead of curing the illness.
The illness being all CC spells and conditions.
Knock down and petrification basically boil down to the same thing: you can attack your enemy without consequence.
Dominion, Charmed, and confused on top of that can make your enemy a friendly and control them.
My suggestion would be instead of making enemies immune to these conditions to change the nature of these conditions.
For instance a knocked down character could get a saving throw every time he or she is attacked to get back up, this would make it less attractive to attack a prone enemy and the ability would be used a lot more for what it is supposed to be used for: crowd control.
Petrification could give the petrified subject a damage resistance of +20 or something like that, so you can attack a petrified enemy freely.
However you will not be doing a lot of damage.
Charmed, confused, and dominated should get a saving throw to snap out of this condition when they are attacked.
This would prevent the ability being used as a combat initiator, since the subject won't be suffering from the condition very long when attacked by multiple foes.
In addition these spells could no longer be used as hard cc, but would require a more tactical approach from the player,only dominating enemies which are not in danger of being attacked by you or their former allies.
It would also fix the situation most POE players have encountered multiple times, where the main tank gets gibbed with one of these abilities.
Just my 2 cents.