Trying to use a shield with Fume might be where you're going wrong tbh. He absolutely is dodgeable, you just have to get a feeling for the timings. His 270 degree sweep is a classic case of where its a good idea to dodge towards the swing and i-frame over it. Go in there and try to get a feel for dodge timings and when you have a window to get an attack (or heal) in. With Fume it pays to not get greedy with attacks, since he can pretty easily either catch you mid-attack animation or you get left with not enough stamina to dodge his combos.

And yeah as another comment said more than almost any boss in the game Fume punishes panic heals. If you do want to heal you basically have to sacrifice an attack window.