1. Every DPS class is an AoE DPS class. I suppose Summoner might be limited to about 3-4 that they can really maximize on. But Monk, DRG, and Bard can all pump out fairly decent DPS on groups -- faster than singles for sure (unless low level). Sure, you should tailor how big your pulls are to what group you have. But don't be the timid tank adding 5 mins to DF brayflox HM by pulling max 3.

2. Similar to #1 in terms of gauging how big to make the pulls. Regarding what to roll for: if it's static/FC, then you've got special methods. But otherwise, I'd just roll if you want it. You put in same effort as these people, so you get same chance at reward. Can do the more altruistic method OP mentioned if you feel like it, but that's just your personal choice.

3. Yep, they'll tell you usually. Or message shows. Just means they will need explanation.

4. OK

5. OK, i guess.

6. Waste of time. Covered by #7 and #10.

7. OK

8. Yep, basic tank role. Requires some learning early on, and attention to maintain in different circumstances.

9. I guess. But mostly just build agro on everything. If your gear is much less than the members of your party, then this becomes more important.

10. OK

11. OK? Mostly I just log off if I'm tired.

12. OK, I guess.

13. Lot of things mentioned. Some make sense to watch, some don't. If you can't change it, then focus on what you can change instead (unless you're in a raid deconstructing why a fight is failing). For example: Ally HP matters for a PLD using Cover maybe - but a WAR can only change their own HP, so focus on that.