Alhanelem makes a bit more sense. Yes you do need HP to survive hits....butttttt...at the cost of you having to try to cure yourself
If you summon a spirit and can get away, why aren't you replacing the weak spirit with an avatar?
The whole point here is to get away. Not to fight. If you can get away and want to kill whatever aggroed you, sure, yes you can summon an avatar. The point in using spirits this way is you can more quickly pull them out in an emergency.