Are you using your creature and/or a summon to help?
Do you have any temporary boost potions you can use before heading into that fight? If not, visit Buad's cellar and see if you have the ingredients to make some.
Have you done everything else on the island? Did you find the cave there under Sassan's grave? Jump off either side of the peninsula to get to it (not that that would be any easier at level 17, depending on your choice of how to complete the quest there).
If you teleport back to Broken Valley, in the far south west you can take the path to the Orobas Fjords, to level there.
Since you last leveled, have you checked all the decent merchants for possible upgrades to weapon(s), armour and jewelry? You may also just be able to enchant / re-enchant your current equipment with better enchantments.
An adjustment to skills or strategy may help...
Character OptimizationThe official "ULTIMATE MAGE" guide
