Others' ships:
On the Conquest, it's a very high-skill high-reward ship. It really shines in the mission, where you use its speed and burst damage to tear apart a much larger Hegemony fleet. It's a good ship that a lot of people have used to great effect, especially with proper support. It's like the Odyssey, but for people who like the green tree better than the red tree.
On the Champion, I thought it was really tough and dangerous on my first go, but struggled to make use of it at any point thereafter. On a League/midline fleet, all I could do was stick PD on it and use it as an escort for something larger. It's too fragile to hold up under fire, and too slow to get out of trouble.
On the Eagle, it's a really fun ship that's just too fragile for late game. Builds I've seen amount to assault (3x phase lance) and harassment (3x IRA or ion beam), with the first getting beaten up in chaotic situations and the second not earning its DP cost.
On the Venture, yeah, it's got a lot of issues. Painful to have to keep alive in that one mission, given that its AI seems to have a death wish, and it doesn't really have many uses besides. Its missiles are passable but limited, and its ballistic/energy mounts combined with its flux stats don't let it do much. It could be decent as a logistics/exploration ship, but it seems to operate under the assumption that its combat value is so spectacular as to make it worth carting around despite significant supply costs and 7 burn.
Invictus is cool, and definitely doesn't have to be a sniper. I'd argue that you're missing out on half of its value if that's how you use it. It should be absorbing damage while also dealing damage, even if not to/from the same ship. You can get really aggressive with it with only minimal escort. Big downside is that there's only one real 'build' for it - it plays the same no matter what gear you use.
My ships:
Gryphons are great en masse, but their AI seems to love getting them killed in smaller numbers. It's a shame, since the niche of 'lobs missiles from behind a tankier ship' could be really cool with the kinks ironed out.
Retribution tries to be a premium Aurora, but ends up being the Aurora from Temu. It'll take some damage in every engagement, has cardboard armor, and needs more planning to ensure an escape route. Other than that, it fills the same role of moving around quickly and harassing targets. Upgrading its armor significantly wouldn't make it OP - AI Retribution is useless right now, and player Retribution needs some kind of edge over an Odyssey or an Aurora.
Shrikes tend to just get themselves killed immediately in AI hands. A player Shrike with a really well-designed build and some red tree investment might do okay, but how long is a player going to be piloting a destroyer for?
Brawlers are another ship I liked in my first run because they seemed well-armed and dangerous, but they're just not that good (aside from the absolutely insane LP version). They're too slow to do frigate things, and their two medium mounts don't really get much done against larger ships. It's supposed to be a tough frigate that can punch up, but it just ends up getting cut up from behind by faster frigates or destroyed by errant fire from its larger opponents.
Centurions are built around being PD escort frigates, but there aren't nearly enough missiles and fighters around for that to be viable (and, even if there were, the AI is unlikely to let it navigate a chaotic battlefield full of threats while also providing effective PD to its charge). It's designed around a role that doesn't really exist.
Cerberus, Vanguard, and Lasher are without a real niche. All but Vanguard just feel completely outclassed across the board - there's no reason to field them. Vanguard is tough enough to be tricky to kill early on, but in later fights, it just ends up getting killed after a short while. A victim of the fact that "slow, but tough for a frigate" is a calculus that doesn't really work out once larger ships show up.