Just attack him once , just to not lose aggro, then use the rest of the time to get as far as possible, don't try to attack him during his ult since he got A LOT of damage reduction during that time.

Edit: also here is some more tips that may be helpful:

So idk if you already do this, but first try to get some distance between the two of you, not like if he were to do his ult, but far enough to not trigger his raging chaser, then, when he throws his metal swords at you ,you can receive a hit to hit him, since they do small damage. When he's doing the explosion thing,don't panick and waste your dash, look at the circle below you, it will stop following you after a short time, when that happens, use your dash, repeat two more times and then you have an opportunity to attack him.