One of the many great features of the Commands and Colors system games is that scenarios do not have to be balanced, since the game is designed to be played as a two game match, changing sides after each scenario ends, even if the tank is too powerful as you suggest, it will be just as powerful for you next game as it was for the opponent last game.
And of course there are plenty of scenarios with no tanks, and a few with tanks on both sides. I imagine that the future expansions will also add plenty of other non tank scenarios too, and no doubt player designed ones will be forthcoming too.
With match play style, you don't even have to play the same scenarios back to back, thought the appeal of setting up the board once for 2 games has its benefits
What I have done in the past, is play a number of scenarios from one side, them sometime later when all is forgotten play them again from the other side, it is interesting to see how different the results can be.
I have played C&C-A, C&C-N, BC(original), BL(original) and Mem'44, and with a lot of experience with the system you also realize that some days, no matter how good your tactics, the cards or the dice or both will go against you, and nothing you do will make any difference. There is a lot of randomness in the system, and tanks, with their all or nothing nature and high unit point value do perhaps make this more obvious.
I will revisit this later when I have played through more of the tank scenarios.
There is also the VP for recon cards often in effect when defending against tanks, which tends to make the attacking player take more chances with movement, and if they push too far on their own and get bogged down near infantry, I suspect they will have a more difficult time.
Personally, if I wanted things to be fair and square I'd play chess or draughts, but we are all different