Hello scrubs, first you have to be a bloodthirsty dude to play IllidanZO.
as a resume :
Yes, his mechanics are simply cancer : Autohit and spam Q;W, sometimes press E when you feel u're being the main focus. Doing this will almost make you a good Illidan player until master+ league.

and YES, you can firstpick this dude but be sure to ban an Auriel/Lili/Sonya, these are the 3 worst counters to your hero. (Johanna easy to dodge, BW high cd on metamorphosis, Alarak easy to dodge etc..)



Why is he OP ?
Well mate, this is because he's casting spells instantly and has a huge sustain ofc, and if you've got enough reaction time/brain gamer you can also add "step 4".
1. use Metamorphosis (R) to tilt your opponents (like dodge a malf ult which is 0,75 spellcasting).
2. perma autohit (when you're not about to get nuked), try to hit and run to create more dynamism.
3. Chase the world when you see an opportunity, Illidan is the best chaser atm, your team will mostly follow
4. -Experienced only; on 1v1, every match up that has skillshot is not a threat if you know their cds, just use W or Q to dodge.


Is he good on everymap ?

Answer is... YES !! Don't listen to soloq haters that prones "Illidan is only good on Cursed Hollow" or smth
because it's wrong, the hero is good everywhere, but SHINES on huge maps. Reason is longer are fights, higher are chances you'll win them (but this is not a condition !).
Also, Illi**** can solo Boss if you time evade (E) well. Before lvl 16, you'll have to spam W only and miss 0 autohit (and take the metamorphosis basic build). It's easier on the new nuke map (just dodge swarm).


The only counter I've met until now on GM league are Double supp setup (Auriel+BW, Auriel+ Lili) when you have no team cc/burst potential.



When to pick The Hunt over Metaphormosis ?

The hunt is used for it's global map control, also it can be useful to add some burst to a Nova/Medivh that spotted a lone but squishy wolf. It permits you to soak exp and still be a threat for ennemies.
Also, you should never take -The Hunt- if their team got at least 5 secs of CC (including blinds/Silences)
because you'll be useless until you are on team league. In that case use Meta to temporize/dodge

Including : Thrall/Sonya (jeez)/ Every auto hit heroes that has spell/talent boost for auto's

Using E is tricky, for example, Thrall can press E to force yours, and crush ur head when it's gone (2,5 sec evade vs 6 sec+ wind fury boost)
So try fake to take some damage before using it