The biggest problem with this is that there's only a small amount of cards to be honest. You can't have rare cards dropping at a common rate, that just makes everything common. Instead of making demands, how about propose a solution? I don't think simply putting the devs on blast because you have not got good cards is a nice approach.
I propose the following;
1) People are starting to reach end game, and/or end team builds. We should consider an expansion set, with new cards, mostly for middle to end game scenario. Reason being is that a lot of the 'better cards' are not really that viable to use either. Putting in another set of mid to high end cards could mix that up again, and put everyone back to theory crafting.
Ie: 5*->6*-7* and 6*->7*->8*
2) Pal points system - Consider putting all cards into Pal Points, obviously 4/5/6 starts are exceptionally rare, but at least let it happen now and again.
3) Gem system rework - Of course these numbers are changeable, but it gives an idea of what could be done.
50 gems - 4* or better - Exactly as it currently is, cheap gambling.
100 gems - 5* or better.
300 gems - 6* or better.
500 gems - 6* or better, chance% of getting past event cards that are no longer in circulation
500 gems - 11 monsters - Exactly as it is.
This kind of setup still encourages the gem system, without editing it too far. It also provides choice for players. Thoughts?
Edit: Hard to implement a card trade system. Especially when you can have 2 devices, and just keep rerolling a new account, get the free 6* and send it across. Repeat. Also, with everyone trying to offload/trade their junk cards, it'll just be full of bad really.