welll NEOxx0, try banish abuse on your lovely warden. wait till the warden is really close, and banish. can't attack and is slow. now siphon mana to lower the warden's mana pool. after the first banish is off, wait a bit for the cool-down to end, and banish again. then you FS. however, the warden still has some defences against this, mainly blink. blink can stop the siphon, and can get away from the FS.
the BM would accually probably fare quite well against the warden, because the warden would constantly have to blink away to stop the BM's spells from affecting her.
and the ultimates are both summons, and neither is truely better then the other. pheonix is really strong, and can usually last quite awhile with good micro (running it away when its hurt, let is die by itself so its reborn). avatar requires corpses though, so you just create it, get max ammount of spirits, keep it back a bit so it doesn't die, repeat till the avatar dies on its own.