Agreeded. Subverters only work in large numbers and against unskilled players. Any player worth his salt can kill subverters so quickly they don't do anything. Gaurdians are much harder to kill, and their synergy with the Progen just makes them sick.
To be honest though, I think you hit the nail on the head in the first paragraph: the flaks have gotten to be too effective and carriers have become obsolete (unless you build bombers and dock them, ready to pound a SB).