Blitz needs help
Biggest issue with him is how if he hits Q, the rest of his CC and damage is guaranteed. The skill already changes his opponent's position entirely, rendering them dead if they're a squishy. There's no reason for three types of CC to be tacked onto it too.
He's a one trick pony, but that only makes his design worse. If he can't land pulls, he's useless to his own team. If he does, he is rewarded too much.
His base damage could be lowered, Rocket Grab's stun removed so whoever he pulls can better react to the rest of his combo, or Rocket Grab changed to not go over walls. I think Riot should start by toning down his obnoxious kit, and slowly buff him into something else. I don't care how iconic his grab and dunk combo is, it has to go.
Bottom line: Blitzcrank's current design is bad. He always ends up frustrating the crap out of one team, being overwhelming or underwhelming. He has no in-between. He's not engaging to play. You basically try your luck at landing Q every 15 seconds and go AFK until it comes back up.