I have spent.... Eight non-stop hours trying to kill death Knight, with two other players each time, and I can't beat him.
Not really sure what the fuck to do at this point. I'm not having any fun at all with this expansion. I just dont see whats "fun" here. I've beaten the base game many, many times. Ive beaten every souls game many, many times, but this shit? Its bad. If this entire expansion is like this, I think im done and i wasted my money. Im incredibly angry right now, and my mind may change, but this is some straight up bullshit.
The trick is to wear him down and don't let anyone get grabbed b/c he heals of that.
Hit him with some Huge firepots, either fly or volcano, they throw off his combo timings. If all 3 of your friends can make them then 3 volcano pots each would be more than enough, just stagger your timings.
You can also hit him with stuff to stop healing but I find that to be a pain.
Also deep sleep pots MAY work on him, I haven't tested.
The light wall attack seems to micro stun him, or so I think. Idk, just saw someone spam it and he dropped to one knee each time. Maybe I'll try that I guess. I know he stands still after his bullshit combos, might try the backstab route. Too irritated to try right now..
It never hurts to go off in another direction and accidentally discover a tool to help you. There's a LOT of crazy good utility in the DLC consumables and key items.
i killed every rememberance boss, but none of the death knights, because i kept getting grabbed and was not enjoying the fight.
I'd suggest to just go elsewhere unless you really want one of the death knight weapons, there is so much stuff to see in the dlc and the scadutree fragments* help a ton, so consider to come back later, if you still want to beat the death knight.
* you can find many without having to kill a single boss.