Full list of releases here:
https://www.guildwars2.com/en/the-game/releases/
But before just before Xmas we had Fractured, which added three new Fractals and a couple of new fractal bosses, plus reballanced some of the old ones. Plus it was the end of the Tower of Nightmares where we finished delivering the Anti-Toxin to the tower in Kessex Hills destroying it. There are new events and champions to kill in Kessex, plus it's still full of Toxic enemies.
December was pretty much solid Wintersday activities, plus they added in Ascended Armour crafting, some new healing skills, a reballanced a ton of skills.
January added in the Origins of Madness, which has the Marionette superweapon event in Lornars Pass (starts on the hour every even numbered hour), Bloodtide Coast has the Wurm event which starts with an escort mission around 10past the hour (odd hours), and the Wurm fights start around 20 past (depending how long escorts take). The Wurm has 3 heads which have to be fought by separate groups at 3 different locations and must be decapitated within a minute of each other to win.
The Wurm is a VERY hard fight, easily the hardest boss in the game, and its not been beaten very often, maybe 5 times total over all the servers.
In addition to the bosses there's a ton of lore to be seen, you can gain access to Scarlet's secret lab, find her diaries, get ideas on some of her future plans. Then in the latest patch they've added a full recap instance where you examin everything that has been going on for the last year and try to puzzle out what Scarlet has been working towards and what comes next... which is going to be something big, and devastating!
Also with the latest patch they added the Edge of the Mists WvW map, which is a huge new WvW area separate to the main WvW event. Points on EotM don't affect main WvW standings but they can earn your main WvW areas additional supply drops. It's also a good place to earn WorldXP to increase your WvW Rank, and is actually a really really nice WvW map! Some great fights going on in there.