Alright mate. If your using frozen throne it is always key to get your shop. Blade master has the best hero harrass in my opinion because of windwalk, speed scroll usually makes using the mana unessecary, and healing salves and potions of lesser clarity ensures that you only have to briefly leave the enemy before you hit again.
Get windwalk and evasion. Mirror image is an alright ability, but compated to his others it sucks balls. Plus because of his bonus damge on top of his critical hit damage when he leaves windwalk he is nearly as good as warden at hero killing.

But im going to assume your talking about w3. I know you already said it dude but most people say it and they talk about frozen thone. In w3 it is almost always better to go mirror image and windwalk. You will be killing a lot less hero. But because of the fact that healing is almost non-existant for the orc outside of tier 3, you dont want your real units to take much damage and the mirriow image helps with the creaping. Plus your hero is going to take a ton of damge as well with only hero life regeneration.