It would be beneficial to add in some -regen and -rech debuffs during the fight. Since the Monster's HP is so large, and since regeneration is tied to max HP, restricting or even flooring regeneration will help shorten the fight considerably. When I soloed this Monster on my Ice/Cold Corruptor, I used a lot of -regen, -res, and -rech. Even still, it took around 8 minutes to solo. If you still have trouble, best thing to do is just increase the size of the team to take down the Monster faster.