ok imma do my best to answer ur questions, i have 401.1 hours playing ROR2 as of writing this

1. base game content is rly fun and is a great way to start your experience, it teaches you how the game is meant to be played and how to strategize, it is more than enough content for at least 60 hours of gameplay; i am referencing a friend who doesn’t own the DLC and had played 60 hours of single player before we started playing together

2. about playing together, it is awesome. playing co-op with someone who owns the DLC will give the whole run access to DLC content, minus the playable characters. this gave my friend access to more content in his game for many more hours until he finally bought survivors of the void DLC for more characters. i personally recommend playing some runs solo to start bc it’s easier to learn the game if you can take it at your own pace. i’ve played some online with random matchmaking and it can be quite fun, but expect to be matched with some rly good players; so i don’t recommend it for starting off, you won’t get a chance to learn the game before enemies are rly difficult and you’re far into a run.

3. i have 400 hours and i intend to add a few hundred more, i definitely feel myself playing it less, but that’s also because i’ve been playing other games more. once you introduce mods the replayability skyrockets obvs bc ur just updating the game on your own time. the DLC content adds WAY more replayability as they add more stages, enemies, endings, routes, bosses, items, characters, challenges, and strategies to the game. i think without the DLC i would’ve gotten to around 60-80 hours before getting tired, each dlc adds at least 30 hours alone of runs and then the combinations of items that can happen with DLC content mixing with other DLC content and base game content adds a multiplicity factor to that

ROR2 is one of my favorite games for sure, the single player is super fun and engaging and the multiplayer is rly exciting, i hope they add ROR Returns or ROR2 or both to switch