I always liked to play Illidan, but before the rework he was just so....frustrating. Blizzard did great job with him :) I like the approach you have focusing on DPS self-sustain. That is how he should be played in my opinion. Great job. I did extensive testing on all his talents and combinations in many games.

As for why people do not prefer Battered Assault at level 1. I think it gives you the biggest damage boost by far, but the trouble is you have to 1v2 to get it, or only engage with a teammate around. Immolation on the other hand gives you lots of wave-clear and tons of damage, even if you are not constantly hitting the enemy heroes. On the other hand Unending Hatred is a late-game oriented talent, that makes you so powerful you can 1v2 the other team easily after level 20.

You might wont to try Hunter's Onslaught at level 7. With the reduction of cool-downs to Illidan's abilities I find it to be much better healing tool in all cases, simply because half the time you will be executing abilities, and that is time you don't spend auto-attacking. Plus you hit multiple opponents with your abilities. Also works very well in combination with Immolation and Marked for Death.

Again good approach. Thumbs up :)