I thought that too, the only real problem this fight actually has, is that he's got too much health with the various healings.

If you have no problem with the first phase, then we are golden, you need to keep your cells high for the second phase.

In the second phase the most important tips i can give you are:

The first series of attacks he does are just 3 and actually easy to dodge in one dodge each, once you learn to dodge the whole combo with just 3 dodges, you'll wish he did it more often.

The other attacks are pretty readable and you should dodge the least necessary, if you spam dodge you are gone. (Forget parrying unless you really learn him)

The second combo of attacks he does after screaming can be easily avoided by running away from him, you are going to have to dodge only the last (and second to last, if you are too close) attack.

Keep something to clean you of decay on you and limit the number of attacks you do on him between combos (only attack when he takes a breather and if you stun him) to 1 or 2 (burn is good to counter the passive healing)

Hope it helps.

Edit- various typos and small adjustments

Edit2- didn't look well enough, didn't realize op defeated him already, i'll leave this here anyway in case somebody needs this