Mustrum_Ridcully
Legend
Of course it's a problem and it will probably cause the issues you mention. In the long run, I'd expect any given group will not have the Simple and Complex Fighter running together.This gets into a key problem area of design theory beyond the core. Does the more you add raise the power level of the game? One of the problems in almost every supplement for any edition has always been potential power creep. It might sell books but it quickly ruins a game as the arms race is never sustainable which brings the edition cycle to a close more quickly. What you are suggesting, by saying the complex fighter of any given level should better than the simple fighter, is bringing that power creep forward from a game supplement problem into the core game, whether in modules or not. Of course perfect balance across the entire array of classes, both simple and complex, is not likely an achievable goal, but shouldn't it be something that is attempted at least for the sake of avoiding power creep and some classes outshining others?
A question may be how big will the difference be - if the complex fighter still has two hit dice left while the simple fighter is already spend out for the day, maybe that's not a big deal. (But will this difference be satisfying for the complex fighter?)
But if the complex fighter combined with smart play cannot outperform a simple fighter with smart play, then there is no point to playing the complex fighter. Doing so is like intentionally playing with a handicap. Some people can probably pull that off in the long run, but I don't see myself as one of them.
4E accepted that this problem would probably occur and gave everyone AEDU. But apparantly, that's an unpopular move and Essentials already tried to loosen this. The next edition seems to go away even further from that. Maybe D&D Next fans will have to accept that they can't have everything and that good balance is not part of the deal? Or would they rather have the complex fighter an unpopular choice because it's a lot of ado over nothing?