Great build and pretty much what I have been using as my go-to since day 1, glad to see someone else appreciating rain of fire. Personally I never loved the dot build because I find that hitting 30 people takes a very long time and often does not happen unless you are one to poke a lot, but I prefer clearing waves with Gul'dan's Q when not fighting.

I tried the drain life build! Epic 1vs1 and especially when the enemy is below half hp that is really OP!

Decent build, though i believe getting talents that buff Coruption with the 1 and 16 and lowering his cd with the 7 talent is far superior in late game when a lot of team fights happen, since Corruption is just to strong, and hitting several enemies 3 times will be very simple once your lvl 1 talents quest is complete.
Your build will be a good strong early game build but fall of hard late game since your is focusing to hard on single target, but relies so heavily on that life drain which has a long cd as well with no other options to reduce it's CD at all.