That's me couple of months ago xD .. Got my Minato kage last sept and always hopes for luck for him to land a devastating AoE rasengan .. I keep buffing up my combo for him to release that AoE rasengan until i read the skill description carefully and from my groupmate's opinion .. If you want to have this AoE rasengan of Minato Kage to work, target those opponents with "Tag" status, you know what it looks like? .. just like what your Sailor Sakura looks like, yellow with kunais pointing at her .. Or else, if you targeted someone without tag, it will only inflict single damage ..

I think you already did the big rasengan attack because all of your enemy's ninjas are all have tag status. maybe you just didnt see the animation or lag so the animation of AoE rasengan didnt show.

He's a russian i think, just judging from his name and if im not mistaken, he said it in one of the threads in GenDis or here ..