@Bright_OpsMaster level or no, if Phoebe turns every other hunter against them, then he's gonna have a bad time. Keep in mind, even if they are NPC hunters, I think even a master level hunter might have trouble with that. Plus, any PC hunters that decide to side with her.
Which she very well may try and do if she thinks Shai is dangerous in any capability. I think most hunters would decide to kill the witch, to be honest.
Not to mention, Phoebe has a few more tricks up her sleeve. She has methods of going
around obstacles instead of through them. He can't watch her 24/7, and she isn't exactly the honorable sort that would chose to fight a target head on if she can help it.
But we'll see, we'll see~