My wife and I leveled through shadowlands together. We’ve done all the quests together. She can use the grapple points in Korthia, the ones you use with the Maldraxxus person during the main questline, but I can no longer see/use them. I used them during the quest just fine but can no longer see them while she can see and use them no problem. It’s the only way to get to one of the rare spawns and it’s quite frustrating to be unable to get over there and help out.
Technically you can use a glider from the chain to get to Relic Breaker. 
But yes, that is frustrating. Sorry that’s happening, this is new to me, no one I know is having this.
Maybe by some chance, do you have settings turned down low? I remember that some of the things that get labeled “essential” are way out of whack. Or render distance? Long shot, but only thing my “helpdesk” part of my brain can think of.
The settings on mine are maxed out. My PC is quite powerful. I can try matching mine to hers though, she’s a bit lower in settings than me. Goblin gliders are something i didnt even think of, so good call there.
I am having this same issue- some alts cannot see!
Has anyone figured this out?
I have two characters maxed and through Korthia. Now two alts cannot see the graple points. There is a quest to start it but NPC is not there.