The speed of the carryall's are faster and unbalanced vs original. When 4 units attack 1 like enemy, original had chance of kill, 5 even chance, in Legacy even 6 like units nearly no kill chance. Slower flight speed and pickup time Doubled or even Tripled would get it closer to original on Normal difficulty.
Results in much harder AI as you devote units and time on 1 or 2 rotating repaired units, even on early levels which is unfair and strange to new players.