You really don’t need a speed build for this. Because it is always near the portal. Yes sometimes it does takes many tries to find one.
This one is setup to do 350. I don’t know if the others are setup to do that.
Plus here is a tip. When I do 100 kill curse chest in bounties. I start the event and port back to town. I go do another bounty. I don’t waste the time standing there killing 100 monsters. I’ll port back later to finish it. Plus if it is on a map I’ll do that 1st too.