it's being a while since i last played (read: more than 1 year), so is RoS worth the money to buy?

Homu homu

If enjoy the lore as much as I do. I spent 4 days to clear the campaign; I was going through the story/side story reeeeeeeal slow.

If you played D2 before, there's few old recurring npc in this game

D3 is a long term game. However, you can still casually play the game. With the "Loot 2.0 & Smart Drop" it's easier to get decent gear now. Unless you're talking about playing on a higher difficulties (Torment 4, 5 & 6)

I play daily; around 3 hours max, sometimes only 1 hour (just login for the sake of killing some time) since 1st week of ROS. I can do Torment 3 casually.

Perhaps you should wait for another month for the price to drop. One of my friend had the same dilemma as you, but she bought it anyway xD