Some mods try to fix any imbalances with faction AI, if one consistently dominates the other(s), but CA will change it themselves every patch (but usually don't fix anything like that between major patches).
For Steel Faith Overhaul mod play throughs:
In my Eltherion (High Elf) game, on the Vortex map, both Eataine (white High Elfs) and Avelorne (green High Elfs) were dominating Ulthuan, while I was off in Southland fighting Orks (I even disable all confederating, with mods, to slow down the Elves, in particular).
Although, in my Grom The Paunch (Ork) game, on Mortal Empires, both Sylvania (Vamp Counts) and Von Carstein had almost all of the Empire conquered by turn 90, when I quit (I dont much like Ork play style, even though it is much better now). I think this is probably my fault, for having confederations disabled, as Empire is most reliant on it and I have seen them snowball pretty hard from it.