Seriously, this is a problem anet is aware of for at least 2.5 years!
http://www.guildwars2guru.com/arenanet-tracker/topic/257919-mouse-cursor-is-missing/
https://forum-en.gw2archive.eu/forum/support/support/mouse-cursor-disappears
Someone in this post describes it best
I had the same issue, there is a trick you can do in Windows to fix the mouse issues rendering horribly on 4k displays by simply having magnifier open, even at 100% (or mouse trails)
But apparently if you run any of those with the game, the mouse completely dissapears. You’ll need to turn magnifier off and mouse trails if you’re using that.
Can this please be fixed? I have been loving how amazing this game looks in 4k, but support has been lackluster at the least, anet won’t bump the size of the interface, and now this?