No new skill lines yet that I am aware of.
The Craglorn group adventure zone has been added, along with timed trials. I don’t have any Veteran rank characters so I don’t know a lot about this.
Veteran ranks have been extended to 14. This will soon be replaced with the Champion system, which is a horizontal progression system compared to the current vertical progression of Veteran levels.
An armor dye system has been added. You gain dyes by completing achievements.
Improvements have been made to the engine lighting system and NPC animations. I think the game looks better than it did at launch.
Veteran versions of several leveling dungeons have been added, and some public dungeons/delves have been made bigger. Also, all solo dungeons scale to your level for more challenge. Group dungeons scale to level of party leader, up to VR10 or 12 I think.
I believe the Werewolf skill line got a rework recently. Stamina-based skills also got updated to be closer to magicka skills.
These are the things I’ve thought of quickly that I read or heard from Twitch streams. From what I’ve read Zenimax has been pretty good about sticking with the 4-6 week release schedule for updates.