I'll post the actual changes to their stats.
Former stats for Khergit Horse Archer:
80 in melee proficiencies.
150 archery, 100 throwing, 60 crossbow proficiency.
5 Power Draw.
5 Horse Archery.
Current Stats of Khergit Horse Archer, post-update:
70 in melee proficiencies. 130 Archery.
3 Power Draw.
2 Horse Archery.
Essentially, this means the Khergits have lost a good amount of their considerable advantages. They can no longer shoot accurately at full gallop, in addition to shooting less powerfully, and riding slower. They are also weaker with melee weapons, and no longer have any shield skill, while they gain some more ability to move quickly on foot.
The changes to Khergit Lancers are of less note, including +1 Powerstrike, no horse archery at all(they previously had 1 point of this), and +2 points in shield skill.
The lancers now look like this:
115 in all proficiencies.
3 Power Throw.