I've had numerous firsts in multiplayer (always with friends), including the Elder, swamps, and Bonemass, so I've had an easier time, as far as knowledge goes, in single-player when I've not had to learn everything on my own.

About splitting up to do different things, one additional advantage is has is the fact there is no lag when the game switches to "single-player mode" once you're far enough from the others. If your multiplayer is laggy like mine (I'm the only European in our group) then it's nice to go off on one's own to gather food or wood or do whatever.

Overall, everything that is fun in single-player (which to me is more or less every single thing) is at least doubly so in multiplayer.
Combat is, indeed easier, as strength in numbers is more significant than the stat boosts enemies get.
Also, it's simply more fun to fight in a group, and even dying can be amusing.
I know we often laugh at at least the sillier deaths, such as getting shot with a lethal arrow while entering a dungeon (tombstone and corpse ended up inside the dungeon).

Definitely worth a try if you do have friends who also own the game. You have nothing to lose by trying.