First of all HJ is awesome. My main gripe with Siralim 3 compared to 2 until now was the lack of control over evening out your party’s level.
However there is ONE small problem with him. The higher level creatures get the same XP as the lower level ones. This prevents the lower level creatures from eventually catching up. This would not be a problem if HJ was active all the time, however he is inactive during god battles.