The dust bag and tags are great to have, especially if you're planning to resell eventually. However, I agree with what everyone else has been saying-- it's not a deal breaker. I've definitely heard that fakers will include real dust bags and tags to try to trick buyers, so it's never a guarantee. Best to take it to LV or get it authenticated here. 
I rotate dust bags between by bags, as I do have one pre-loved LV without a dust bag... hoping to work up the nerve to ask for an extra one next time I'm in a store!
I rotate dust bags between by bags, as I do have one pre-loved LV without a dust bag... hoping to work up the nerve to ask for an extra one next time I'm in a store!