I think the biggest problem with the game is currently the way unit levels affect gameplay. Per unit level, a unit gains 10% life and damage, this doesn't sounds like that much, however the these effects stack and it takes effectively 1.1^2 = 1.21 (about 20%) more hits to kill a unit if it gains one unit level.
For 2 unit levels this becomes 1.21^2 = 1.46 = ~45% and three level 1.21^3 = 1.77 ~75%.
Note that at lower ranks (up to gold), the effect is less, since one can win with a better balanced deck and better micro. If you look at the tiberium league, you need to have lvl 10-11 units to have any chance. For new players this is/ becomes also very frustrating, since they can be matched against unit levels that are way higher.
Even an experienced player with a new account probably would take months to get to master league.
A possible solution would be to cap the effective level difference, i.e. damage is capped as if the unit dealing damage is max 2 levels higher. A variation of this would be apply diminishing returns (e.g. 1 level difference -> cap of 1, 2 lvl diff -> cap of 1.5, 3 level difference -> cap of 1.75, etc.. by halving the benefitrs per level).
This could further be combined by reducing the gains per level from 10% to 5% (still resulting in an effective 1.05^2 = ~10% gain).
I believe such an approach would not remove the incentive to have a level advantage, while at the same time making the game more attractive for new players.
