I am not at all happy with Corvettes as they are currently implemented...
They are very strong against LRFs, and are supposedly countered by flak (which also counter LRFs)...this is the same situation that marginalized LFs in Diplomacy (which were countered by both LRFs and an LRF counter, the HC)...
There is one other instance of this: the bomber...flak counters fighters, and both flak and fighters counter bombers...this counter, however, works out differently than the LRF/Corvette example above because flak is a "soft" counter against bombers and the flak/fighter counter is one the hardest in the game....
This type of counter, where A counters B, and both A and B counter C, is extremely problematic...the only way to prevent C from being marginalized in this relationship is to make A counter B really hard (which just ends up marginalizing B )...
The other fundamental flaw of Corvettes is that they are a jack of all trades unit...with their composite weaponry, they are great against structures, caps/titans, and frigates...with their anti-light weaponry that targets SC, they are also great against SC (particularly bombers)...additionally, they have ability debuffs that weaken their target...it's like combining the best qualities of 3 different ship types into one, and giving it limited weaknesses (basically, flak and AoE abilities)...
Corvettes could be tweaked so that Corvette Spam isn't as powerful, but doing so I don't think will change the fundamental problem with this unit...