Guild Wars 2

Let’s say I join dungeon run already in progress (and don’t get kicked immediately for playing necro :P). How can i get to them, other than on foot? Only by waypoints?

Yes, only by waypoint.
But remember that you don’t need to enter the dungeon portal, if you waypoint anywhere in the map the dungeon window will popup for you.

And once inside the dungeon itself, there will be waypoints unlocked at certain checkpoints of the dungeon. You can use those to catch up to the group rather than running all the way to them.