Major Updates / Changes since August?
Check out https://www.guildwars2.com/en/the-game/releases/ for details of previous releases.
Do you mean changes that are still in the game or also all the “come and gone” Living Story things you missed?
Imo the biggest new things that didnt go away again are ascended weapons + armor, two raid mobs and a new unlimited WvW area, alongside a nice amount of class balancing and new heal skills (fairly meh ones but hey).
Oh and if you used to hang around in LA afk a lot, right now you even get loot while doing that!