coming from someone who played almost exclusively offline/single player, yes it is worth it. It is more challenging by yourself as it makes everything more high risk. Even playing with just one other person makes the game incredibly easy as you have someone to back you up. Just think of taming a dino, two people means it goes down twice as fast, not to mention while the dino is chasing one player the other player can attack the dino. It is a lot different when you only have one player.
Meanwhile in online mode, everything i gathered, tamed, or crafted was stolen or destroyed literally every single day. Everything you do is utterly pointless unless you are in a large tribe, which good luck at getting into those.
For me, the game was only playable in offline mode. I know a half a dozen people who play the game, none of them play in online mode because the community is cancer.