Dota 2 FAQ : Is diffusal a good idea on Windranger against a Wraith King?

I can't tell if the mana burn is significant enough to burn the mana I need to burn once I have it, i've been getting it a couple of times in this matchup and putting only 1 point in my ult to burn more mana before he falls. I think it's gotten him under threshold a couple times each game but i'm not sure.

Probably not even bad. The Focus Fire with a level 2 Diffusal Blade should not only burn mana really quick, it's probably also enhancing the damage significantly. Definitely going to try this out, Wraith King or not.

Windranger has a BAT of 1.5
Focus Fire gives max AS, which gives you 1 attack every 1.5s/5 = 0,3s.
You get roughly 3,3 attacks per second and burn ~67/120 mana per second with diffu1/2.
Necronomicon active burns 125 / 175 / 225 mana, passive 25 / 50 / 75 per hit.

Necronomicon is probably better: it gives str and int, the summons do mana burn, and offers a lot more utility for your team. Diffusal Blade gives primarily agility for stats, which is basically wasted on Windranger.