It would be much easier for Musketeer DPS branch into 2 jobs, one healer (using smaller guns like SCH use diferent books), another one DPS. If they give Chemist something like the Mix command that functions like Mudras they can even add more skills then normal, just like Ninjutsu.

Also I don't know why people are using NIN as the other DPS we were promised. Multiples jobs have to be more then 2. Lets not forget the chick with a rapier in the artbook cover.