I never dismiss just Dave's insight, even when I disagree. I'm sure there are some things I'm missing about the character. I do think he's missing some stuff too. He's all negative. I'm all positive. I'm sure Tremor rests someplace in between.
Tremor's not a zoner. He's a grappler with rushdown and anti-zoning.
He has a great D1. Check out its reach and recovery. For how far it reaches and how quickly it recovers, its pretty fast. Its not the best in the game, but its very close. Now, check out the reach on his grab. It almost has the same range as Kotal Khan's Sun Throw. Now, do his D4 - which is the best in the game.
Now, get into his combos. You'll notice that most of them move him forward. Now, start cutting them short and end them with D to B 1, and hold DB to access the low ... safe.
Anti-zoning - I can't really speak on Metallic or Crystaline much, but Earthshaker is good for beating out zoners - especially spammers. That aerial low beats out projectiles. Then, you have a low and high projectile. The low one sets up the high one because the high one beats airborne opponents. You can also tap back after any projectile to roll back - and it costs no stamina.
He is wildly unsafe, but he has enough tools that your offense is hardly ever going to get snuffed out once you devote a little time to him.
I do think he's more execution heavy than most think. You want your combos in the upper 30's and lower 40's; Not down in the 20's. He's designed to do big damage off of just about any launcher and you can hit confirm into everything. Once you've conditioned yourself to down to back for his ender, hitting the right button is easy.
If they're blocking, just end with D to B 1 and hold DB to push them away with a low. If they're not, you still D to B but just launch with 2 instead. There seems like there are gaps in his strings, but there is enough hit-stun and block-stun to keep him safe. Just don't finish his combos generically and hit confirm everything.