Ah, sorry, I think I was being vague and which is why you misunderstood me. The AoE damage after Decrepify explodes a target ally will deal damage to your own units (and probably allies). I know the missile is supposed to target allies, but again, the AoE damage can hit friendlies. So, is this AoE damage intended?
Also, something I just remembered. The Whirlwind slowly spirals into the center, but once it gets to the center, it sorta stays in place for about 10 seconds. Iunno if you wanted it to be like that, but I kinda liked if it got to the center slower or began spinning outwards again, once the center is reached.
And, I forgot to post my comments on the heroes in general.
I found the Grim Rider to be the more fun of the two. Decrepify is a neat spell and I really liked the Whirlwind. Perhaps it could use a new name, not sure what, though. As for the Archon, I'm never a fan of melee heroes, so I am biased against them. I feel like the ultimate might be too strong for him.