Their archers are also made of glass, and literally any cavalry will crush through their mediocre infantry meaning bad news for the archers. They also take less cities and castles on average than sarranids. Vaegirs are solid but are lacking in their infantry putting them slightly behind sarranids.
(Huscarls are still better archer counters, but because nord vet archers do basically nothing that is why they are statistically worse than rhodoks). They have garbage archers and in the field nord infantry are actually outperformed by rhodok infantry. The nords statistically are just worse rhodoks. Rhodoks are great at defending hill based areas but struggle to move out towards open field, thus being less viable for conquering the entire map. Every other faction aside from swadia is hindered in some way, be it lacking cavalry, only having cavalry, terrible infantry etc. They have one of the best troop compositions overall, having decent infantry, and well above decent archers and cavalry. They are the most successful ai faction, statistically owning more towns and castles than any other faction in my playthroughs.
Ive actually done the calculations and overall the sarranids are the best faction. If the player is sided with a faction, that is the strongest faction, so I will be judging on faction performance without the aid of the player.
Ive answered this in a previous thread, so I just copy pasted my answer over