I think I've said it in other threads, but imo, you can balance best, when extensions and modules work on a principle of diminishing returns, so, for skills, bonuses are applied based on your base level, eg a 3% bonus is 3% of your base level, which means the bonus is exactly the same for each level, but in % terms it decreases as you add another level to the skill. At the moment you have increasing skill cost per level which is fine, but its offset somewhat by the exponential increases some skills give. Maybe if that was done, the % per level of skills would need to be adjusted to take account of the lower bonus it was now giving, but I don't really see a problem with that.
The counter argument to this, is that you've put a lot of EP into that skill, so you should have a 'significant' advantage. I don't disagree that their should be an advantage, but the primary concern has to be overall balance. To be healthy the game must pull new players in, and encourage them to stay. So you have to both allow new players to compete, whilst still giving them something to look at as a long term goal in terms of skills, etc. So skills have to be useful without giving game breaking advantages. I think my suggestion is one way of doing that, there may well be others too.
Specifically on the issue of the Tyrannos / Ictus Shield tank, it seems to me that there is a problem, on the basis of the rock, paper, scissors nature of combat balancing in the game, with racial ammos only doing certain kinds of damage, etc. Assuming that system is staying, then surely the blue bots should get some kind of ammo that is more effective against shields? Since the fact that you do kinetic damage is irrelevant to the preferred tank of most Green bots.