Basically its close to impossible if you just learn pure priest skills. You can do it in easy mode, but I dont think so in high difficulty mode. There no damage skill on priest path, where summons cant actually act as main attack power, even together with your creature, especially while during the final battle. Going bare fist will make the case worst, which it has the lowest damage output, as without damage enchantments or additional stats from weapons. I will assume that your pure priest will not had any skill from other branch such as warrior, ranger and mage.
