I tell people to watch the cutscenes if it's their first time through. You only need about 5 people to finish Mainline anyways (and can still finish in about 20 mins) and I'd much rather people watch the cutscenes and have the run take longer. The cutscenes are great and some of them like in Bahamut are as good or better than the MSQ.
If it's your first time. Watch the cutscenes. You can do the dungeon for the fights later.

It makes me sad when people rush new players or new players quit because they are stressed about not keeping up. The story is great. Enjoy. Veteran players can suck it up.