Along with everyone else, I see incredible value in having multiple jobs in different categories. I started as Bard, but after my first run through coil, I started a BLM. Bored with the long wait times for DF, I moved to CNJ and leveled WHM to 50. Needing a tank in the FC and with another party member doing WHM, I completed WAR. Since I'm balancing and not putting all my eggs in one basket, leveling multiple classes into the iLVL's past 90 means choosing who gets the cool stuff first. WHM=96 while the WAR and BRD are a lowly 93, which only a few weeks ago was still pretty darned high. I am now leveling an ARC since this gives me both another healer and DPS to play, so I'm already collecting and saving gear and atma stones for them as well. (BTW, all three mains have atma weapons, and I'm working on Animus for the WHM first. For some reason, they won't let me carry a book for more than one class at a time.)

I find that having a job in all 3 categories gives me a different perspective for each fight. It's like when I play guitar, bass or sing with a band. I know where the melody is going, how the the rhythm is played, and what the counter-melody are doing. What's really cool is that someone from my FC or any other FC can say, "We need a <healer or tank or DPS> for <name the fight>. Want to join us?" I apply the appropriate set and I'm on my way. If I'm looking for tomes or XP or gear, I can drop into PF and if there's something interesting going on, I'm there.