I think the GTVA have better weapons than that by now anyways. There was quite a fight onboard the Iceni ("Shivan bodies are among the dead..."). But the Shivans win anyway, they have lasers. I doubt the GTVA can match that without having to lug them around. The Shivans pee lasers.
Doubt it. The Shivan we saw took three or four seconds to charge up before firing, and fired at range where it would have been easier just to slice the guy or smash him.
With a casuality figure in the thousands, we have to assume there were a
lot of dead Shivans for them to stick out much. Arbitrarily assign the Iceni a crew figure of, say, 5000. Of these, very few will be marines, because for most purposes, marines are dead weight. Call it 100, perhaps 120 to make a full company. (This is probably too high; a platoon of 50 or 40 is much more likely.) Assume that there are 200 dead Shivans for them to be noticible (probably more honestly). Ship's crew would be useless in a fight, they're not trained for it, and they wouldn't be armed either. Still, say they account for...20 of the Shivans. This is unlikely but I've been generous with my figures so far, so why not?
That still means 120 NTF marines, who've been training to fight other humans this whole time, and not really very good marines otherwise they'd be deployed somewhere more useful, took down 180 Shivans. They traded at better than 1 for 1 in the conditions Shivans are superbly equipped for fighting in, and more importantly, they aren't. Anything really powerful will punch through your internal bulkheads and possibly ruin ship systems to the point a successful defense of the ship would be rendered pointless, so the best weapons wouldn't be issued for this sort of duty.
Weapons came a long way, or body armor did, or both, because apparently even when not trained for it and not equipped for it, the average marine in FS2 can go one-on-one with a Shivan at knife-fighting range and come out on top.