Yeah, I've always looked at the Tarrasque and thought weaksauce, this needs a worldkiller breath weapon and Wolverine regen powers. Seriously though, depending on the party maybe it isn't big enough.
I'd probably make the regen more as well. After all a troll regens 12% of it's HP every round. A tarrasque recovering that much per round? That would be a little over 80. Now we're talking a monster that's tough to kill!
Yeah, 5e needs more Kaiju action to balance out the inevitable power creep. Maybe we need to kitbash a towering metal colossus to do battle with Tarrasque-zilla. Something with a sword the size of a wizard's tower and serious DBZ powerup beam action. Kamehamaha!
As part of a larger homebrew project of mine, I made a variant Tarrasque that uses some previous edition abilities (e.g. Aura of Earthbinding) alongside a few of my own additions (e.g. Powerful Blows). I didn't include a beam attack or anything like that, but I did add an improvised attack that encourages DMs to throw buildings at their players and stuff as needed. I hope you guys like it.