You can avoid mindgate resonance by exploding the opponent's gate
So far i never lost a game against mindgate using opponents (AI or PVP).
I lost many times against dune scorps, ruby dragons, lava golems.
Probably this is just the style of deck i usually play.
Anyway, mindgate is not at all threatening for this style, and a card is declared OP only if it threatens too many styles.
well pretty much any mono or duo aether deck will take mindagte, as well as 90% of Rainbow/all quanta decks so I'd say that soon this may occur often, also many decks, specifically rushes don't cary perm control cards, but may have one or 2 steal or something, so I'd say give it a month and this resonance thing may happen a lot more often
this is why increasing the cost or limitng the number of turns it can be used should happen now
5 turns seems pretty good, that's 5 extra cards, if these 5 have mindgates then you are well up
Limiting it to 5 draws will not harm decks that aren't specifically trying to create huge decks, and limiting it to 5 isn't going to harm any decks either