All right. Mercs and the other guys are now in, as are some notes about damage types. Also rewrote a few descriptions completely and made changes to light cavalry. Some surprising findings here.
The Swadians have always been touted as having good heavy cav and archers, and indeed we see that that is true. However, they also have high-ranking offensive infantry and decent light cavalry. This pattern suggests that Swadians are best suited for aggression - charge everything forward and let the archers take care of themselves! In sieges, it might be better to send Highlanders in before the expensive Barons. For siege defence, unless you happen to like paying your noblemen to feast in the hall, it might be good to purchase a small garrison of mercenaries.
Like the Swadians, the Vaegirs have good bowmen and cavalry. Unlike the Swadians, they have no good infantry but have surprisingly capable horse archers. This may mean that they should mainly field mounted troops and leave the archers at home, except that'd be a waste since their archers are the clear #1 in Calradia. The player has options not easily accessible to the AI though - on-field fortifications can keep archers fairly safe against cavalry (but watch out for fast infantry!), and mercenary tanks can be hired. Like the Swadians, the Vaegirs can use their knights as tanks and as frontline besiegers, but it might be less expensive to hire mercenaries to soak up damage.
I'd always thought the Khergits were good for nothing except their horse archers. As it turns out, their foot archers are also very good units, as are their light cavalry. Even more of a surprise: their defensive infantry are quite capable if not stellar. Looks like hit-and-run does
not have to be the only option for the horsemen of the steppes after all. Their castles also are not quite as easy to conquer as they seem to be. They might have some trouble besieging the homes of others without mercenary help though.
Nords - no surprise here. Awesome infantry, pathetic archers, no horses. Players may want to look at Mercenaries and Sword Sisters for four-legged friends. Role-players may choke at the notion of putting so many females in easy reach of the savage berserkers though.

The turtle nation of Rhodok does not surprise either. Top-notch infantry and archers, all but useless horsemen; again, consider hiring mounted help. That said, I did not realise before looking at the numbers that the Rhodoks actually are really, really good at not just fort defence but at taking castles too.
The Sarranids, being the new kids on the block, always did seem kind of mysterious to me. Now it's clear that they are arguably the best horsemen in Calradia, with top-ranked heavy and light cavalry and horse archers only slightly less frightening than the Khergits'. Their foot troops aren't worth much, though their archers should do well in castle defence if protected by mercs. Attacking castles on their own would be a pain, so consider outsourcing.

As for non-faction troops, we see that Sword Sister units are all of average worth, as are most Mercenaries: good when you don't have a top-tier option. Mercenary tanks and knights are excellent though and every single faction could benefit from having one or the other (or both) of these on board.
I hear the Black Khergits have been nerfed, but they're still competent horse archers who are terribly difficult to off. Slaver Chiefs, on the other hand, only look impressive: in reality, they are limited in many ways. Still, who wouldn't want to have elephants in their army? They're also possibly the best units to crush infantry and archer lines with, so the Rhodoks had better watch out!