I need a bit of advice on creating a witch to be a boss in my campaign.

I have a 4 player party that will be level 7, intended level of this boss is 10. I have a fighter, gunslinger, magus, and monk.

I haven't been able to find a witch npc, so I created it using pc rules as the gmg suggests. He has an ac of 28 and 118 hp.

Does this seem too low? My fighter could crit and potentially take him halfway down in one hit.

Also, does anything on the spell list or feats/actions seem too strong?