You don't need 3 others to beat Dalamadur. Find 2 people you know that's already cleared it.
Just need to learn to time the super dive so you can avoid it's one shot.
Yeah, beating it is actually pretty easy I think (you're referring to the giant sand-worm thingy that you fight on a boat, right?). Also, there appears to be a certain bug with that fight that allows you to carve it multiple times for loot, in which you carve it once on each side up to 5 times. Was how I got my brand new armor at least.