I've reversed my opinion on turrets, they are a bit very game-breaking in CTF.

Do rockets do bonus damage to turrets? They should. I think that would be a very elegant solution to the turret problem. They'd still be good, but it would help stop turret clumping, and would give rockets more of a use. As it is, there's almost no reason to get a rocket instead of one of the various types of bombs.

This was the bug I was having, Hempuli:
I couldn't leave red spawn. It was very odd.

Turrets are generally pretty easy to take out, especially with bombs. I don't see turretting the opponent's base as being that much of an issue. Sometimes, though, it seems like turrets will lose track of who set them up, and dying to them will give messages like "ƒƒƒ was killed by !". When this happens, sometimes the turrets will be impossible to kill, which can make things a bit difficult.

On a different note, would a minimap or some other way of viewing more of the screen at once (camera scroll, maybe?) be possible? It would help a lot when you're using the cannons, or when you're trying to find your flag and return it to base.

Speaking of returning the flag to base, it seems unintuitive that you can capture the flag without having your own team's flag in base.

On yet another note, the builder seems to not be seeing very much use, and I think there are a number of factors for this (note that changing all at once might overpower it):

It's a very slow vehicle, which makes getting it to where it's needed a time consuming task

The blocks that the builder creates are very fast to dig through, like dirt. It might not hurt anything if they took as long to dig through as mineral patches

3 minerals for a block is a lot, especially when your team is losing, which seems to be one of the times where the builder can be most useful.

All that said, the builder does seem to have two uses: Sealing off a trench to help ensure a victory once your team has taken control of the game, or building some walls to help defend from incoming vehicle/flag stealers.