I think eco system is ok as it is now, and is should work totally fine when all the classes would be balanced. Now you are usually choosing between 2 spawns with a good unit or 3 spawns with weaker one, and that is ok. The problem is, for example, that cheap cav class, that cost less than 150g is undisputed overwhelming compared to, for example, 160g heavy inf class. Cheap skirmisher classes have more ingame impact on their own than heavy inf, that costs more. When this class balancing would be done, it would fit that eco system perfectly (just as it was on previous patches).