All players who attack a siege vehicle should now get credit if it is destroyed.
Previously this worked similar to tapping a mob, where the player or raid that first tapped the siege vehicle would get credit. This made it harder for multiple raids or ungrouped players to complete Stop the Siege!. This change should solve that problem neatly.
Daily quests Slay Them All! (Horde) and No Mercy for the Merciless (Alliance) have had their PvP kill requirements reduced to 10 from 20. NPCs defending the fortress and south towers now count toward these dailies as well.
Enemy players have the same tapping mechanic as mobs, so even though a player can get Honor from a tapped enemy, they wouldn't count towards completion of the aforementioned quests. Similar to the vehicle problem, ungrouped players or those in smaller raids would often come up short of the requisite 20 kills during one battle. Obviously, changing the tapping mechanics for players isn't the solution, so Blizzard made the kill requirement lower and included NPCs as valid targets. The latter change is probably aimed at lower population servers or realms where Wintergrasp participation isn't too high, as well as realms where there's a distinct faction imbalance.
The number of NPCs defending fortress has been increased.
Again, this should make it easier for players to complete the daily quests as well as move up in Rank. The NPC guards don't hit hard and have very low hit points, so they're really just cannon fodder for quest and rank requirements. I'm not a big fan of too many NPCs in a PvP zone, but this change seems to have been necessary. Players on defense often hole up in the fortress, slowing down offense's rank gain. Having more NPCs lowers the effectivity of that delaying tactic.