The upgrade problem can be solved by, well, MATH.
IMO we need to revamp the approx. level formula. Right now it is plain addition, right?
Multiplication and peicewise-defined functions will solve a lot of things.
All numbers can be changed:
There could be a base lv of 30 for an elemental with 100 HP and 0 ups.
For HP: (a)
0-100 HP: (current HP/100)^2.5
for 101-300HP: (current HP/100)
for each extra 20HP above 300, add 1 to (x)
For Marks: (b)
(Mark multiplier)^0.6
For Card Draws: (c)
(Card draw multiplier)^0.7
Upgrades: For every 13.3% of the deck upgraded, add 1 to (x)
Resultant lv: r = 30*a*b*c +x
You could smooth the function out if you like. Basically what I am suggesting is that add a quadratic-to-cubic multiplier for HP at low HP (1-100) so that this cannot be exploited. For moderately high HP the multiplier should be linear. But to prevent ridiculous numbers to be created, for even higher numbers, the HP should follow the current addition system. For mark/card draw multiplier, since the marginal benefit of having those diminishes, adopting a concave curve makes sense for determining level.
Here's my 2
.
Oh, and, back to the unused card problem:
Some cards are just plain outclassed, and not redeemable by any meta shift. See cockatrice/giant frog, or phase salvager/ball lightning, as 2 examples that came right to my head. Meta-shifts will only make cards that at least occupy a niche become a centrepiece. But for niche-less, statwise-sucky cards, they are screwed up beyond all repair for normal battles. In every CCG, there are always a batch of cards that belongs to this desolated corner. The only situation they will be used is as substitutes of their big bros if the player has no access to that particular big bro. That is, if graboids are banned in an unupped environment, haematite golems may see some use. This kind of restriction can be enforced by restricted pvp tourneys (which IMO should not exist in the forums only; a free-for-all tourney with special rules could be incorporated into the main game), or subtly by random pools (draft battles anyone?). If those kind of play are available within the game, even rubbish vanillas will have a niche in restricted play. EVERY NEW CARD will see some use even if they're out of normal play, if that is so.
(Yes, I'm adopting a milder stance to card making. New cards have their uses, but restricted play is the only way you can MAKE SURE that they add value to the game. Think of phase salvager
As of today, adding new cards to the game is merely a gamble for an increment in meta diversity)
Well another 2
. Together you have 4
from me