Yep, in Balance Mod the Norse spearmen line in particular is buffed. This change couples with religion changes: the pagan player now suffers large recruiting penalties in Christian fiefs, which represents most of the world.
So basically the new balance is that the Norse have the overall best average of troop strengths, but recruiting is tougher. Meanwhile, the Christians have wider recruiting possibilities and many more centers to recruit from (located conveniently in Britain, while the Norse recruiting there is subpar because of Northymbria being mixed in religion), and if you take the best troops of the various Christian factions, they can form an army superior to the Norse (ie, gaelic and anglo saxon troops combined is the best combined force in the game). Of course traveling widely to recruit is somewhat more hassle than the Norse have in returning home to Scandinavia, but recruiting for any individual Christian faciton is a breeze (multiple towns and conveniently located compared to Norse).
The hope is to also get away from the Norse swordsmen Saxon spearmen powergaming model, and in particular to actually encourage use of the full line of Norse troops (ie, with Norse spearmen in their prior state, there was little reason to ever promote to anything but the swordsmen). The old balance made sense faction vs faction, but with religion changed to exert a dramatic effect on recruiting, it no longer made sense to balance by considering faction alone, but rather by a combined consideration of religion and recruitment difficulty.
In sum, Balance Mod basically works like this:
Troop Strength: Combined Christian Army > Norse Army> Individual Christian Faction Army
Recruiting Convenience: Individual Christian Faction Army > Norse Army > Combined Christian Army
Also, the Norse AI lords recruit somewhat more elite armies than the Christians. This is to create more of a Great Heathen Army burning through Europe feeling, and couples with individual balancing to the eliteness of Christian factions (ie, Wessex recruits a little better than Mercia and East Anglia, while the picts/irish/britons have particular patterns to the composition and concentration of their forces). It also couples with conversion changes (Christianity spreads more effectively than Paganism in Balance Mod), and initial garrison changes (larger initial garrisons to slow early conquests).