So, you know that guy already. I will tell you about his 2 tactics. One vs One, or One vs Two - and on the other hand One vs Many.
From the start! Very useful tactic versus melee, and one-two targets is leveling Drain with Terrify. Drain in early game can outdps, any melee damage dealer, and much to that you will steal regen health! Combo drain+fear is most powerfull weapon on close combat with Fiddle. With Ranged DD is worse scenario becuase they can go out of range pretty fast. Crostorm is old story, get out from bushes, exhaust on B, put Fear on target A, and start draining from target B [closer to you], in that way you can get double kill easly.
Second tactic is One vs Many - Leveling Dark Wind and Drain/Fear is base. Dark Wind on 5 lvl bouces 10 times, its sick in close combat and makes fire in teamfights - last time on 1v1 Annie summoned Tibbers - too bad there wasnt minions nearby - I threw DW It bounced like 5 times and she died. Using it with ultimate is bit more job - Put Crowstorm on face of enemies, If there are minions in your arena, WAIT FOR THEM TO DIE, then put Darkwind, Fear, Exhaust, Drain and GG, triple in your pocket.
Of course, all o that is theory that in 85% works for me, when you jump out of busheh you will be most likely aimed by everyone, so work of team mates are priceless. Or use them as first meat, and you will wait calmy to use ultimate - that works in 95% :P See you around <3 Hope that helped even a bit