Yeah the only time we see a Diomedes survive is I think in Artemis Station, where it IS carving up the Cormorant, but it's doing so alongside Steele's battlegroup so it's not that impressive a feat.
There's a Diomedes in that scene?
...
Okay, yeah. Not the best of impressions.
I thought those TerSlashBlue's were from the Atreus?
Either way, in that scene, the point is more along the lines of "Steele's battlegroup effortlessly swats aside a Karuna as it charges the de facto capital of Jupiter, with none of his ships even slowing down and most of them not even bothering to pay attention to it as it's skewered by a few auxiliary beams from a the Atreus and Imperieuse.
I'm not sure what seems more pointlessly suicidal---the Renjian's Leeroy Jeeeeeenkiiiiins into the 14th BG (even against a UEF equivalent, it would have been a quick and pointless suicide) or the Comorant's dashing (sideways?) charge into a state-of-the-art GTVA battlegroup in formation and in optimal firing position and range. Even for a desperate delaying action, did the Comorant's CO really think that any of Steele's ships would even have to slow down at all? At least the Nelson was trying straight for a ramming attack and had four Sanctus cruisers as a distraction...
Salty, try to set up a Diomedes versus a Karuna, with both ships in optimal position.
The Diomedes rips the Karuna to shreds in about a minute, and finishes with over 50% health.
Now try it with the Diomedes coming in under the Karuna, which can't bring its main guns to bear.
The Diomedes tears the Karuna a new in about a minute, again, except this time it finishes with over 80% health.
The Diomedes is a scary ship. They just suffer from consistent bad luck (and being on the wrong side of the fight from the protagonist).
Okay, I'm a tad confused here---Aesar, a Diomedes has more anti-ship firepower than a Chimera?
Really?
Slash beams rarely do full damage, and it's a pretty narrow angle for a Diomedes to get all four of its slash beams even capable of firing on the same ship at all (at angles like this, they tend to be more inaccurate regardless).
A Chimera's 3 MBlue's do ~59,400 damage per salvo, which can fire once every 35 seconds. A TerSlashBlue has a refire time of 10 seconds. A Chimera has a much easier time of bringing maximum beam firepower to bear, as it just has to place the target vaguely forward of the ship.
And, of course, a Diomedes is larger than a Chimera by (IIRC) a big margin. And it's a newer design. And apparently significantly more expensive. Though come to think of it, a Chimera might actually be a better fit for eventually replacing the Deimos, as it has incredible AA capability, sufficiently flexible and quite powerful anti-ship firepower, and enough speed and durability to at least be on par with the Deimos. Though being smaller and cheaper, they're still kind of distinct in terms of role and usage.
Anyway: the Diomedes is a big ship, and seemingly expensive. I would hope that its collective firepower would be more than an average Chimera's, given that said firepower can rarely be brought to bear on the same target. The ship feels more like a pocket destroyer or a battlecruiser than a typical corvette, though it still has a puzzlingly small anti-ship armament for its size, era, and cost.