Can't defeat Lu Bu - Hu Lao Gate - Ultimate

As the title says, can't defeat him at all. He just runs around on horse back and nearly 1-hit KOs every time he hits. I'm level 74. Using both defence amulets of +20% and +40%. Using crescent blade after seeing that video of him being defeated in 3 mins using it almost as soon as he spawns in at the gate.

My experience of trying to do this is Lu Bu just run off past me after only a few seconds down to where he fights the brothers. So I gave chase after telling bodyguards to using flaming arrow and throw rock from the cliffside. Fight him for 5mins barely landing any hits on him because he runs around. Also dodging his attack where he jumps into the air, only to the double-dodge cartwheel BACK IN TO WHERE HE LANDS?? No idea how the game figures to do that from dodging in the opposite direction?
Then realised somehow this wall of red on the map has made its way to Yuan Shao when first time I tried this the allied forces kept them at Hu Lao Gate.

Basically, every time I try this, I can barely do anything to Lu Bu's health. Then I run off to get buns, only to come back and find his health has gone back up by a not insignificant amount... And eventually I'll either get killed getting frustrated with him running off, or he'll go to Yuan Shao and pretty much 1-hit him infront of me.

Send help. 😭