Drugging is not the problem, I do not like it, but OK, it is a part of the game. Just to be sure: M4 = M3 + microupgrades. Am I right? For example, I have Isida M3 (microupgrades 50/50) and Mammoth M3 (microupgrades 33/50). I think it is not bad. And I am dead with enemy (Isida M3 and Hunter M3), although I have "full health" at the beginning of the fight, he does not use drugs and nobody helps him.

That is not the truth. Not in all, but in many free games, there is used a principle "pay to get a better chance to win". In the Tankionline, it seems to be used the principle "pay or lose".