I usually wait until I finish doing an area before I decide if I go back but that Bothrium beast is keeping me from wanting to go back. You can keep his difficultness but that immunity to stuns needs to go, cause no boss that is meant for solo play should have that kind of difficulty.
To all those saying they love the difficult challenge of it I`m glad your enjoying it, but remember if to many people find tough then there less likely going more places like this.