There is no question that Corvettes being overpowered or not is a huge debate, both in-game and on the forums. I am not going to make an absolute proclamation such as "Corvettes are not OP. Git gud." Rather, I am going to present my argument for why Corvettes are not overpowered.
Data and Evidence
To begin, I am exclusively a Medusa player. I have 45+ hours on the Medium Corvette, that being the Oberon line. For a few weeks now, I have been recording and uploading 95% of my matches to Youtube. You can find my channel and the videos here, and I present these as evidence that skill and experience determines success far more than ship class. For the purpose of this argument, I have gone through the ending scorecard of the 104 Veteran matches I have recorded and compiled the following spreadsheet of how often each ship class ranks first, second, and third on the enemy team. I did not include Team Elimination matches because they are very different from Deathmatch and Onslaught. (Note: I must use the enemy team's scores, because my team's will be skewed by my own performance.) (If the image doesn't show, click here: http://imgur.com/YLJAvSS)
I'll start with some disclaimers and observations. With 104 matches, it is not a huge sample size for such an important question, however 104 matches is still a large enough pool to see trends emerge. It should be noted that Tactical Cruisers are hard to measure because they score points by healing instead of kills most of the time, which is different than the other classes. Also, while counting up the scores, I immediately noted the overrepresentation of Destroyers, as well as a large number of matches that had Destroyers taking all three top spots. More on this later.
Corvettes make 1st place 20% of the time, which is what I would expect for a game with 5 classes. While this percentage is higher than that of most of the others, it is nonetheless a whopping half that of Destroyers, which clock in at 41% 1st place showings.
When you expand to consider the top 3 spots as a whole, things smooth out and 4 out of 5 classes are nearly identical. The exception, again, is the Destroyer - as usual, it makes top 3 twice as much as Corvettes.
The data simply does not support the claim that Corvettes are OP. Perhaps slightly better than TC's, AC's, or DN's in capable hands, but I can't make any hard conclusions of that manner from raw scores. In the next section I will explain the reasoning that accounts for the data.
First, as I have been saying in other threads, differentiations need to be made. The situation in Recruit is very different than Veteran. I don't have data on Recruit, but assuming that Corvettes "dominate" more than they do in Veteran I can offer this explanation: Maintenance has incentivized Veteran players to play Recruit to ensure a steady supply of credits that is not taken away by maintenance nor the kick-to-hanger bug. When more experienced players go into matches with presumably fresh into the game players, they are going to dominate. Because newbies don't have the knowledge and experience to deal with the Dover (the only Corvette in Recruit), they end up dying by it a lot. Thus, we have a situation where the Dover is OP due to Veteran player backflow into Recruit. The fix is to change the reward incentives and keep Veterans in Veteran, which I hope Battle Readiness will do.
In Veteran, we've seen the data that says Corvettes do not dominate but are actually quite similar to the other classes. Yet in matches they feel so overpowered. How is it possible to always get roflstomped by a Corvette, yet empirically they're not dominating matches? Consider the Corvette's role. It is made to sneak behind enemy lines, take out a ship, and run. It's the ship that preys on people who wander from the team, and it's the ship that takes out the entrenched and otherwise unstoppable Tactical Cruisers keeping the enemy team alive indefinitely.
Corvettes are not responsible for their victim's lack of skill. You can watch my videos to see it in action, the weak ships that wander alone (Tacs, Arties) are fair game to be shredded because Dreadnought is about team play and sticking together. Additionally, when you are in a group, a little attentiveness goes a long way. If there's a Corvette taking out one of your ships you need to be aware of your surroundings and respond appropriately. Watch my video "Impenetrable Defense" (Episode 41) to see what I mean. A strategy that usually works against unaware players is routinely thwarted by people who stick together and pay attention. In summary, if you lack the skill to deal with Corvette attack patterns (which are fairly predictable once you've played with them for a while) I can't help you.
Corvettes need to be further broken down into their three classifications. The Light and Heavy vettes are similar in construction, both fast ships with firing arcs limited to the front. I see the Heavy as, well, a heavier version of the Light. The real difference is with the Medium, my ship of choice. For a detailed analysis, see my guide to the Medium Corvette but I'll sum it up here. It is slower, bigger, and has around the same health as the Heavy Corvette but can fire 360°. Each Corvette comes with a tradeoff for having high burst damage, and that's their health. A well prepared team will destroy a Corvette that's attacking their group, because they cannot tank damage.
Understand that a nerf would cripple Corvettes.
Nerfing damage: They would no longer have the ability to destroy a target before they themselves are destroyed due to their low health. It takes skill to surgically eliminate a ship behind enemy lines quickly and efficiently, then escape without losing all your health, and even then the most skilled Corvette pilots (like myself, frankly) don't have a guarantee of survival.
Nerfing speed: Speed is the Corvette's main defense. Since its shields will last but a few seconds against direct fire, they rely on getting in and getting out quickly. I usually only survive because I'm able to duck behind cover. Make the Light/Heavy Corvettes slower, and they become a niche vessel only good for picking off lone targets. Make the Medium Corvette slower, and it becomes useless.
Nerfing shields: For a Corvette, shields are last resort. Yes, they block 100% damage but remember that they deplete very fast, even when not being hit. In my guide I advise Corvette players to make use of engine power more often since shield power is incredibly precious. Most commonly, I'll be making an attack and suddenly come under fire which is going to destroy me in seconds if I don't act - thus, I pull up shields. They only last for mere seconds, but it can be enough time to get out. Any bleedthrough just makes them moot because it defeats the shield's purpose on Corvettes.
Again, this is all documented in my videos which I encourage you to watch.
I've made my case for why Corvettes are not overpowered but rather ships with a specific purpose and definite weaknesses, backed up by data that shows they do not dominate matches.
What about Destroyers?
When I started to tally the scores, I was expecting Corvettes to be leading slightly, but I was surprised to find that from the start, Destroyers were far and away the most common top scorers. Why is that? Consider this: Which class can take a beating and dish it out too? Which class can use many varied types of modules? Which class strikes an excellent balance of tanking and maneuverability?
They are the jack of all trades, rounded in all stats to provide a ship that's neither squishy nor slow nor lacking in firepower, compared to the other classes. Just as the naval term Destroyer was originally short for "Submarine Destroyer," in this game it should be short for "Corvette Destroyer." Yes, the counter to the Corvette is the Destroyer. They have the modules to decloak and slow down Corvettes, the speed to keep up, and the firepower to rip them apart. A well prepared Destroyer piloted by a smart and attentive player eats Corvettes for breakfast. They can take on every type of ship and adapt to many situations. I'm not going to make the "Destroyers are OP" argument, but as it stands they are certainly very powerful. Perhaps people should consider shifting their attention from Corvettes to Destroyers.
If you've got a legitimate counter-argument to make, I encourage you to make it. I only ask that you avoid mischaracterizing my argument (strawman), equating anecdotal evidence to hard data, or making an unreasonable argument, eg. "Corvettes can destroy any ship before it responds and tank the whole team shooting at it and run away while keeping its shields up the entire time." Let's keep to reason, evidence, and logic, please.