Cloning Ability with increased autonomy

[Weiss Schnee]

Also take in to account that the summoning time for one of his un-dead is Five seconds in which he can direct but not control any others that he has summoned.

Erm, sorry, Minato, but Raal directing his undead IS controlling them.
The thing restricting Raal at that point is his inability to do anything else other than summon another undead, basically making him a still target.
Raal can only control them directly, hence the strain on his mind.