I don't see it as a problem. Sure, a ftr4/barb4 is worse than a ftr5/barb3 most of the time, but a wiz4/clr4 is worse than a wiz5/clr3 too.
Personally, I like starting with ftr1/barb1 or whatever, then taking one class all the way to 5, then evening them out a bit. That way you're only behind...