I think it's a little too good. I would suggest removing the "until the end of Vertigen's next turn" duration on the prone condition. Maybe even remove the recharge from it, as this power could be absolutely devastating with two or three lucky 6s.
As is, assuming a melee character fails his first save, he's essentially stunned for 2 rounds (can't stand on the first round due to the duration and wastes his turn if no one is adjacent, then a single move action on the second round to stand and his turn ends thanks to daze). Ranged characters are potentially in a better situation (they can still attack) but will provoke opportunity attacks from adjacent enemies (because they can't escape).
IMO, it doesn't really matter that the attack itself causes no damage because it's extremely efficient from the standpoint of both economy of actions and bonus damage from opportunity attacks. It might be okay as is if you play the enemy a little stupidly (surrounding the melee while ignoring the ranged), but if you play them smart (ignore the melee and focus on the ranged) and especially if you get a lucky roll or two (recharging Vertigo Sickness about every other round) I think you could have the makings for a TPK.
IMO