In order to see what would happen if we had an ample supply of quick cards, I did a little analysis to decide how much it will cost to guarantee an uncommon draw each turn.
The result of my analysis is a quite simple equation; if every common card slot in your deck is a Quick card that costs X resources, you can expect to pay 2X resources every round in order to guarantee at least an uncommon draw. (See the bottom of this post for an explanation of how I arrived at this result.)
Currently, common quick cards cost a single resource and have an additional positive effect. I don't expect this to be the norm, but if we continued making Quick commons at this cost, the end result would be that you can guarantee at least an uncommon every single turn at the low price of only 2 resources per round. That is INSANE. No other deck could compete with this, in my opinion.
If we raised the cost to 2 resources per quick card (like Magic Portal), it would cost 4 resources per round. That's equivalent to staring with 1/2/2 facilities. That seems to me like a fair exchange to guarantee at least an uncommon draw each round.
If every single Quick common cost at least 2 resources (like Magic Portal), I think we could keep the metagame okay. There would be no need to add in more changes to keep common Quick cards fair.
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[CALCULATION IS BELOW - feel free to skip over this part]
If you're interested, here's how I arrived at the average resources paid per draw:
Every time you draw a common quick card, you can pay X resources to have a 32% chance of drawing an uncommon (29%+6%/2) instead. If you fail to draw an uncommon, you get to pay another X resources to have another 32% chance. For ease of calculation, let's assume it is 33% and not 32%; this rounding up will make the final result slightly low.
This makes a sum of infinite series: X(2/3)^1 + X(2/3)^2 +X(2/3)^3 + ...
In general, this geometric sum reduces to X/(1-2/3)=3X. (See the example at
http://en.wikipedia.org/wiki/Geometric_series for why this is so.)
But you don't always draw a common; you only draw commons 65% of the time. If you round this to 66%, then you will see that you only pay the cost of common quick cards 2/3 of the time. So even though the geometric sum has a limit at 3X, on average, you will only pay 3X(2/3) = 2X.
Therefore, if every common card slot in your deck is a Quick card with no other abilities, whatever the resource cost of that card is, you can expect to pay twice that much on average every round of the game in order to guarantee you always get at least an uncommon. If every common slot is Renewal, for example, you can expect to pay 2 gems every single round on average. (Unless you discard, of course.)