It's not unblockable online. I consistently block it in Doomsday mirrors (or against characters that have Earth Shake-esque setups like Joker). Just ask @
Immortal Kombat.
If a Doomsday player can consistently block their own move, other people should level up and do it as well. If the connection is shitty, then that's excusable. But in a good connection, it's not.