The problem with Relius is that he can't make his doll do high\low moves while he himself is doing a blockstring, like Carl does. The doll's only high\low moves are specials which require Relius to do a pose, so he can't do anything to keep the opponent still.
So, it is up to Relius alone to do mixup, i.e. 6A overhead, jump > airdash into high or land into low. This isn't really great mixup to me.