For the portal you have to move away and then move back after the buff ends for it to register you.
For the first imp phase cataclysm bug I believe it relates to whether you interrupt his first cast of the curse or not. He seemed to wig out if i interrupted it but cast cataclysm as normal is i did not.
My biggest advice is buy a purification potion and just practice outlasting him. if you can make it past all his phase rotations to where hes just repeating the imp phase over and over the fight becomes a ton easier.