Ive used this build several times on other heros trying to find the best hero for the build and i think i have.
Demon hunter: very strong hero, with enough health and str gain to offset the 10% hp hit from ele mastery. He has a very high agi gain and just enough intel to make his defensive work.
The skills:
Pulverize
Lifebloom
Poison strike
Innate: hp bonus
Elemental Mastery
Why do these skills work well?
Pulverize is my favorite agility farmer, it does ok early on and has an amazing wrap around after level 16 or so. Lifebloom is fairly mana intensive but it is the only thing you spend your mana on aside from item use effects, and a great heal. just 1-3 ranks of poison strike cuts down on int kiting, and ele mastery is.... great.
How should this build be played?
Basically grab a fire orb and run to the center, you should be able to clear 3 spawns beacuse you will be able to use life bloom at least once. try to get lvl 6-7 first duel and have a fire orb, infused cloak, and the best pots you can buy. Try to win the first duel, so you can get your ele mastery quicker, after that dont worry about winning hte next 4-5 duels, just farm up and play the late game.
Items:
Starting items are pretty rigid,
Fire orb
infused cloak x2
one ring
cloak of the fox
mastery of the ring
super sonic ring
scepter
2nd cloak of the fox
ring of the speed demon.
From here you have a nice amount of hp, alot of dmg, and good move speed. go into whatever best suits the game.
Counters?
Id say an early spell build wth ganking potential would cause issue, my item order gets fast anti gank items so just watch the mini map and play safe.