A few months ago, NPC skills were updated for each NPC type for balance purposes (detailed in the linked post, for those who missed it). The promised HP update to NPCs level 10 and higher has just been completed by Zhao, so HP values are now accurate for NPCs that are unable to level further. Wounded NPCs have also been healed to full in the process. This only affected max level (or higher) NPCs.
Lower level NPCs that have not leveled since the NPC template changes may experience automated HP adjustments when they level. That concludes this series of NPC updates and there are no plans to make further template changes at this time. In the future, some of the less useful or redundant NPC types may be merged with other types, but nothing has been conclusively decided yet.