I think non-reflectable meteor is fair. It is very costly ultimate and it can already be blocked, dodged and mitigated very easily. Nightblades can cloak it. Templars can cleanse it. DKs can block it.
The only thing OP about meteor is it still has a knockup/down CC. Dmg and unreflectability are consistent with other skills within meteor's classification as a ground based AOE with initial burst hit
Hmm then why is overload reflectable ? Why can a NB cloak out of the meteor or why can it be purged then ? If ultimate are supposed to be all powerful as your saying then all effect that would negate