Army are too cheap to form and AI gets influence easily... So it's kinda imbalanced currently.Honestly I don't see the Army mechanic being a problem. Assuming AI don't have a bonus to influence, I haven't noticed an imbalance in that mechanic.
The problem is that individual lords keep escaping, respawning and coming back at full-steam within a matter of minutes of game time. Makes defeating massive armies a rather trivial accomplishment. Feels grindy.
I guess you already know about this thread
Since 1.5.10 prisoners escape less (can be 0 chance if you have the correct perks) so this aspect of the game is improving.
Personnaly I don't mind about lord respawn (it is core mechanic) but more about them charging back with an army of recruits...