Rotation
Prebuff:
Pop a potion and wait for it to hit 37 seconds remaining (you will need this!)
Netch - Sub Assault - Scalding Rune - Barbed Trap
Then the rotation begins and remains:
Sub - Winter's Revenge - Flame Reach
Sub - Unstable Wall - Fletcher Infection
Sub - Degeneration - Ult
Sub - Scalding Rune - Winter's Revenge
Sub - Flame Reach - Unstable Wall
Sub - Fletcher Infection - Degeneration
Sub - Barbed Trap - Netch
Repeat
NOTE: If your sustain is fine, in place of Sub - Trap - Netch, you can forgo the Netch cast and do Sub - Scalding - Trap