this seems more on the lines of trolling, but I'll answer it anyhow.
A real gamer (Not me) would let DB run an hr on 40, then 45, then 50 and time/count your XP for results
IMO - you need to go with what kills faster. I can do 62's in 12-15 min depending on shrines, map, density and then it will miss 1 or 2 die more frequently take 20+ mins.... Bad for XP runs even though higher GR
I can put my barb on max speed and do sub 5 min 40s. I prefer something in the higher 40s where its still a 6-8 min run but exp is better.
Also for XP run you should try to cube Leorics crown and socket a ruby in helm
and then the secret is stash all your GR keys. Let DB run a rift find an XP pool, run a GR, run rift find an XP pool etc... you'll always be running on dbl xp