We've seen a few instances of healing. We know that Injun Joe is the best healer around.
In Full Moon, Harry had a belt buckle that let him keep fighting when he was worn down and exhausted.
Ebenezer had those magic stones that ate pain and allowed Harry to keep on going in Blood Rites.
Harry pulled the "Put the pain out of your mind" trick in Dead Beat.
Evocation causes one mental stress box to fill up when you use it. So I think that the Belt caused Harry's Mental Stress boxes to dump, so he could keep casting.
Maybe the stones or the others let him set aside his consequences (or consequence Aspects), empty his stress boxes, or gave an extra mild consequence?
I did just find an instance of some pretty significant healing in the book Harry's Godmother healed him after a confrontation with the Nightmare in the third book
but considering who did it, it may not be something that is in the reach of PCs.
You or your GM will have to wait until you have the game in hand, read our discussion of why it might be tough, and then decide if our ideas of why it's tough hold water in your version of the Dresdenverse.
ah well, we'll have to be patient.