Raiders:
They are the weakest and are apparently meant to be. I still don't quite get why - yes, they shouldn't have heavy warships but I still don't see why they should be forced down in power at a given priority level rather than simply only having low priority ships.
It's not all doom and gloom - the Battlewagon is quite nice, and in small games so is the strike carrier. Utter turd that it may be in a direct fight, it is (a) quite tough, especially against beam weapons and (b) the cheapest fleet carrier in the game. Unfortunately whilst this is a nice trick, the fact that it's stuck with Delta-V fighters to support makes it still a bit iffy. Even more so because upgrading to Delta-V2's costs quite a bit (especially compared to upgrading Starfury Novas to Auroras, which gives Early Years EA the same benefit for free!)
pak'ma'ra:
It's not initiative so much as CQ, which makes critical repairs annoying. But, redundant systems makes them tough, plasma webs make them efficient swarm-killers, and as noted plasma torpedos are just harsh. The porfatis is a very tasty bomber as well, quite capable of pummelling a mid-weight ship in packs without coming anywhere near AF range. The pak'ma'ra have a bit of a blind spot for well-armoured, interceptor equipped opponents, but then so do the vree and you're never going to see them on this list!
Drazi:
Boresight = bad
on the other hand
Swarm = good
The two more or less cancel one another out. In theory. In practice it's awkward as whilst you can out-swarm someone in the movement phase, firing a single sunhawk's weapons for every destroyer-class ship the enemy fires means that you cede initiative in the shooting phase (meaning losing a lot of ships before they get to fire). Drazi whateverbirds are ok for durability but not fantastic.
Firepower is very good if you can boresight (solarhawks stand out as borderline insane!), but nonexistant if you can't. This may change, of course, so P&P may see a big boost for the Freehold.
More to the point, there are still alternatives - the Darkhawk is much more flexible and packs a nice missile volley and the Guardhawk has gone from being a joke in first edition to one of the best fighter-killers out there. Escort and AF 6 per patrol point is just wrong.
The weak point it the bigger ships, which do tend to be underpowered and a bit critical-vulnerable (lose a random arc - you have a choice of boresight or forwards, both are a big, big problem)
Abbai:
I can kind of see this one. 8" range secondaries aren't easy to get shots with, the fighter is awful and the combat laser only does so much to compensate. At 15" it's pretty short-legged itself.
Shields are a big plus - in a game where criticals matter so much, having 8-12 damage that can't cause criticals gives you some nice protection.
The fighters need escort protection to achieve much but that's ok because they're not exactly going to be doing strafing runs. If you just think of them as a way to extend the range of escort's anti-fighter firepower you've got it about right......note that you've got a nice cheap escort frigate as well as the big, slow bimith.
All in all they're just unable to do enough damage - they tend to have a similar number of attack dice to other race's ships but without the damage multipliers.
The Jucaya is the obvious exception - and is a very, very nice ship.
Also, if the regular ships are tough, the Marata diplomatic transport is ridiculously so. Granted it's armament is pretty feeble - 6-8 twin-linked AD depending on facing - but it's fast and hard to stop. Try using them as blockade runners and watch the swearwords.
Brakiri:
I agree - I don't know why the brakiri are in here, really - they have all weights and specialisations of ships you could want; a good escort that can hold its own against lighter ships if needs be (halik), a cheap atmospheric assault transport (ikorta), a scout (shakara) - and with AP weapons rather than twin-linked you actually benefit from a scout, two fleet carriers (brokados/cidikar), a swarm-clearance ship (takata) and a number of very good quality gunships.
Their ships are tough, and the falkosi can act as interceptors (and some ships have them already). Slow-loading but powerful beam weapons is a nice trade, and regardless of what the fleet book says, the Haltona and Tashkat more than make up for any lack of manouvrability. In fact, slow-loading beams work fine - a salvo from a number of graviton beams is able to do two turns worth of heavy laser fire in one turn....meaning the enemy isn't there to shoot back next turn!