I would prefer at least using Magic Missile as well over giving a melee-er flight, but between the two I think Lenny with his better chance of bypassing DR (Power Attack, Higher BaB, Str, Greatsword, etc) would have a better chance then Rocky trying to Sneak Attack.
Gods no, this would be a very bad idea, giving a melee flight is proberly one of the best options open to be party, it being able to move the fight up to the Erinye and put some pressure on her, while spamming low damage-easily resisted magic missiles is only a singel step up from using fireballs.

Problem about fighting Area of Effect-using monsters is if you divide enough they have to try and concentrate on certain targets more, along with the healer having to travel further just to heal a fallen comrade.
Problem here is that allmost all monsters can easily outdamage whatever healing the healer might be able to do, meaning that its normaly better to try and finish the fight as fast as possible, and then heal up afterwards.

Also, when fighting AOE monsters splitting up is something you have to do, if they can hit the entire group anyway, then splitting up will reduce their damage by around 3/4.