I'm not convinced boarding is a valid enough tactic to build an entire fleet around it. Firepower seems preferable, sure a boarded ship is worth more, but you know what they say about a bird in the hand, vs. two in the bush.
With any ship other than galliots, I'd agree - boarding is either an opportunistic thing, or else a way of 'giant-slaying' (a handful of smaller ships can still prove a threat to a dreadnought if they can drop their entire marine complements on it).
However, if that's your view (and it's a justifiable, understandable one), then galliots are not really for you. Putting one or two galliots in a fleet simply doesn't work because they're so easy to kill. Yes, they're a fire magnet but they're not a tough fire magnet compared to other things you could spend the points on.
If you do want to build a fleet around boarding actions, they become much more impressive.
Also, in some cases you really don't have much choice but to go boarding-heavy. See the previous comment about giant-slaying; I honestly don't see any realistic way that a Vuldrok Dreadnought with a Shielding Rune can be hurt by any Kurgan ship short of boarding them.
The Kurgan Sheerkhur and Vuldrok Froljir and Myrkwrym strike me as the three best for this sort of thing:
Froljirs are tougher simply because armour can't be bypassed or burnt out and are stupidly manouvrable. Admittedly they risk damaging their armour (because you will be using
All Power To Engines! - it's a boarding fleet, after all), but a 5+ to lose one point of armour isn't the end of the world - I doubt it'll take you more than two turns to close or there's something seriously wrong going on. They also have an extra grapnel gun on the flanks, giving you some insurance against ham-fistedness preventing boarding actions.
You shouldn't overlook the Mrykwyrm in a boarding fleet, either. Point for point you get the same number of troops as a galliot fleet, but 1/3 of them are elites, and you're faster.
Sheerkhurs are less manouvreable, more vulnerable, carry less marines and have an even more guff armament. On the other hand, 4 of those marines are grimson marauders - so it effectively carries two more than the Froljir (and anyone else, for that matter), and you have access to psychics, who can further boost up your troops.
If I recall, the Hazat Galliots are actually heavier armed than the Frigates, making them better at being frigates than frigates, but at a 50% price increase.
True. The big advantage is that one the barrack decks are empty they can still make a meaningful contribution to the fight.