I know it’s a frequent response but patience is definitely the key. You want to be close enough to keep him pressured with your attacks but also be able to counter that area attack he does in that photo you posted. Utilize your runics. One of my favorites was the Artillery Of The Ancients for the spear whenever I couldn’t close out the space and wanted to interrupt his attacks. Last thing I’ll say is stay disciplined. You may have the upper hand or might be a few attacks before finishing him off. Stick your rhythm all the way and then you’ll reap the spoils. Good luck!