What else wouold they have? I mean an Excalibur boosts how many weapons and given it's bulk it had plenty of room for armor.
Or....
New materials and armor patterns developed pre-SSW 1 and were used. Thin, but just as effective ne?
Funny, I was thinking of the Tomahawk and saying, "Look at all those weapons - where's it got room for armour?"
Anyway, where does it say they are so heavily armoured? Maybe they skimped? There's got to be a reason why they get blown away so easily (besides plot.)