Illidan is unique. He’s a great Hero, super strong right now, but I guarantee you that your team will lose. He requires a pretty specific composition and some babying from the Support, which is pretty easy to achieve in coordinated team. But soloQ is like the wild west: every man for himself. In fact, it’s probably better if you just pretend you don’t have teammates at all. They won’t be able to keep up with you anyway. I mean, it’s better than having to yell “team?!” after you die in every fight; you only died because the enemy Hero was broken.
Try to lend a helping voice in drafting. If you’re unlucky enough, your Hero League team won’t draft a Support at all, because God knows, we needed that Gazlowe “support” more.
The best way to lose with Illidan is to make sure you’re way at the front ready to dive into the back line. The closer you can get to Heroes with stuns like Muradin or E.T.C., the more quickly you will die. Try soloing a Sonya or Thrall for fun; you can win, trust me ;).