Thinking about returning and have some questions

[Niwashi]

The bonus from Duty Roulette is only once a day, though.

There are two bonuses for Duty Roulette. The main bonus that everyone can get is a once-per-day bonus. There's also a second bonus available to those filling the most-needed role (which is usually tanks, occasionally healers, but virtually never DPS). If you're in one of the needed classes, you can get that secondary bonus as many times as you care to keep running it.

Yes, dungeon exp was increased but if you plan to play as DPS, FATE grinding is still your best bet due to extremely long wait times.

Well, the other effect of Duty Roulette being added (and in fact, the reason why it was added) is that it has significantly reduced the wait time for getting a group. The people you need to run a dungeon with you are being given incentives to run it. It's still a much longer queue for DPS than for tanks or healers, but it's not as long as it used to be. Tanks and healers can get into most dungeons almost immediately. DPS typically around 15 to 30 minutes during peak hours, maybe a bit longer if you play during off-peak hours. Still, it's better than the several hours wait they were starting to get on the less-popular dungeons before DR was added.