Tomes are the only annoying daily I do on my alt, as I gear both my main and alt for FCoB. The benefits are definitely there though.

1) Being able to gear multiple jobs with lockout gear.
2) Experiencing endgame content with multiple jobs.
3) Diversifying your experience with a difference race, sex, affiliation.
4) Certain financial benefits (Ixali dailies come to mind).


Really, it comes down to how much time you want to invest. Getting a fresh character through the main story and to level 50 will take about a week, and gearing it to 110 will take another. Capping tomes on 2 characters means 12 dungeons per week of exp roulette, if you do nothing outside that. It becomes a lot work after awhile.