All it does is prevent you from summoning dragons and other high cost cards.
Thus prevent quite a few of decks of using a combo - or even playing cards. Also decks that depend on things such as fractalling will be hurt badly: you can fractal a good monster, but you can't really play more than 1 a turn.
If you would only need 2 cards to cap it would be very OP - 3 I indeed consider on the vedge of UP, however as I said: you can't really increase it without making the shard counter basically anything. If 2 cards would limit the quanta to something like 13 (which is when a shard would limit the quanta by 5/12th - just a very little bit more than 1/2) getting those 2 in the start hand would simply cripple any opponent if his creatures aren't drawn the first 4-5 turns.
I think the price a bit low: 2 of them shouldn't really be playable on the very first turn (From towers alone). Maybe increase the price by 2/1?
Hmm wouldn't overdriving it when it gains 45 hp be very strong then? - kill 3 permanents and gain an almost unstoppable creature back. (heck obvious things such as reverse time would only hurt you more).