Try replacing all the "Turret" lasers with Prometheus S on something like a Deimos. Then try to kill it. You'll get ripped apart in seconds. Even something like a Fenris will seriously beat you up with proper defence weapons.
I think that if the blob turrets fired quickly, they could be quite an effective anti-ship weapon. As-is, they're a waste of space. If they were proper, powerful plasmacaster turrets (like they should be for ship-to-ship weapons), then they'd fire at the same speed or faster, but do much more damage with each shot. They shouldn't be able to hit fighters/bombs if that's the case though....
MatthewPapa: Shivan beams are far more advanced than Vasudan beams, which are more advanced than Terran beams. All Shivan beams fire at a fixed location, whereas only some T-V beams do that (the SGreen, LGreen, BFGreen, LRBGreen, SVas and LVas). The beams on corvettes (TerSlash, VSlash, LTerslash) slash across the target. They tend to damage more systems that way, but do less overall damage than the fixed beams. That said, they fire much faster (once every 10 seconds or so, as opposed to about every 30s for the fixed beams) so the damage is pretty even.