To OP:
I fixed your post a bit, to conform more with the guidlines. (Believe it or not, you will get better replies if you stick to the regular layout, and use correct grammar ect)
If you are still looking for a response, I would add a poll with your suggestions on how to balance it.
To OT:
Personally, I think Mindgate needs no nerf.
You can't just put a mindgate in a mono aether, and call it a day. It needs good stall cards, and preferrably some control just to slow down their opponent untill it is ready.
If you can get a mindgate set up properly, with the quanta and ability to use whatever youre given, then you deserve the cards you get.
(It may be worth noting that Mindgate will get slowly weaker as more pillars are replaced with pendulums in duo/trio decks as there is no way of copying the mark)
If the advantage is of cards, why is Pandemonium not OP, since it is the equivalent of using chaos seed on all your opponents (and if you didn't plan too well, your own) creatures?