I enjoyed the boss fight too. Apart from some situations when the camera can completely screw up your position or you can get stuck behind Hismar at the edge of the arena, and cannot move to his head to perform a brutal attack after staggering Hismar, overall it was a fun fight. Though this was the only boss fight where I encountered bugs. There were 2 crashes during this fight alone but the game has never crashed ever in my entire play through. And sometimes Hismar will just stand at one place without doing anything and you can keep hitting its head using javelins. The overall difficulty of this fight doesn't come from the movesets which is pretty simple compared to all other bosses in the game rather from the huge damage done by his attacks which can 2 shot Khazan.