Swadian Royal Swordsmen are beasts, definitely; they really should be, for what they cost
The Nord Axemen and Spearmen are a bit flimsy, but they have a lot of missile weapons and they do pretty well when you have enough army skills. In the next version, they are always going to have missile weapons, so they'll be quite shooty, if a bit inaccurate, and probably well-worth using.
Rhulg are, well, Rhulg. Kind of the epitome of "hard to kill", they can frequently take storms of missile fire with nary a casualty.
My favorite atm is to stack Legionnaires in front of pikemen, halberdiers, whatever. The metal shields take a heck of a pounding, they have missile weapons... and if the line behind has grenades, that's pretty much the end of a cavalry rush right there, other than against the Rhodoks. Against Rhodoks, use Gaucho Pikemen instead; if you put them on Hold fire until the first wave gets into range the results are frequently pretty good.
And then, for sheer cheapness, there's something to be said for having a giant pile of cheap Khergits that you literally don't care if they live or die.