I was just wondering when people would ever use his knockback over his stun. Maybe if you're being chased, but the stun would probably allow you to put more distance between them and you anyways. I guess to throw someone in to a Tempest / Chronos ult? I just haven't come up with really any good situations to use it in.
Before anything else, the blast projectile travels fasters than the stun projectile. Sometimes it can be useful, maybe to knockback a swiftblade before he starts spinnin (he can wait till you throw your slowass stun to press Q).
If a damn aoe hero is in the middle of your team, like a torturer with impalement/ult (or someone just like him), you want to knock him away from your and your teammates, a damn stun is not enough.
Well, the knock back is just one more tool for MoA, make sure to use it...
Knock somebody up a cliff/into trees etc. It will probably take them longer to get out/back than the stun would last if you do it right. And you only want to take somebody out of a fight while you focus down their team. (Like a farmed carry or tanky hero).
Knock them into AoE abilities (including the green acid bomb). Come from behind and knock somebody into a tower/teammate.