I think for many or at least me its about internal balances. I feel that the armys are pretty well balanced between each other sure some are a bit stronger some are weaker but personally I haven't experienced anything extreme. But internal balance is another problem, can I play Tohaa without sukeuls and kaeltars? Sure but I am handicapping myself. There are just some units that are to useful to have so other similiar units in the same army won't really get any use.