One last minute guide that I made after seeing Ziggy's video on Exile Levelling and the AHK script, updated my Hierophant POB with levelling trees and thought I'd share:

https://pobb.in/mxCAiEfLtyp4

I plan to level with Rolling Magma into Wintertide Brand till level 38, where I swap to Ball Lightning and continue using it from there. ~~Muling Arcane Surge from Witch is probably worth it if the servers are stable tonight.~~ brainfart, you get it from vendor after Mercy Mission.

It's not a record breaker but it should be pretty decent, if Wintertide Brand starts feeling bad in Act 3 you can switch to Ball lightning earlier, I want to wait for Unleash but in Sanctum I swapped at 28 and it was OK.

EDIT: I also ended up using Creeping Frost to some extra single target during the Wintertide Brand section.