A rough calculation says 18/24s got at least a 6-10% damage increase vs +3 destriers depending on their armor layout with the patch, not counting leg/headshots, but increased accuracy seems like a far more likely explanation, unless someone messed with/accidentally rolled back soak/reduction/speed bonus.
Haven't noticed anything weird with the damage on NA though.
What periods in time are you comparing, exactly? Post 3.3.9.1 to now should be a decrease, as it would have less wpf.
I noticed that my horse was taking more damage sometimes, but it might just be a few more strength or long bow archers on at that time.
Pretty sure this is the case. Whenever I play I try to mentally take note of what items I see on the battlefield. Since we've been doing a lot with bows lately, I've been particularly focused on those. When the first patch came out, I noticed a drop in the number of long and rus bows. When the
fixed system was implemented, not only did long bows and rus bows resurface, it seemed like 1 slot bows were being used less frequently as well.
Likely what happened is you got used to to your horse consistently taking low amounts of damage from archers (due to few long/rus bows) during the 0.3.3.9.1 patch, then when the newest patch came out and the tables turned, things undoubtedly looked much different.