This is just what I've observed in the past week -- the meta's rapidly changing so what you'll see next week could very likely be different.
What is the generally/most used 6 man setup? 3 dps, 2 support, reinhardt? How does this change on attack vs defense?
I've never seen a team run with more or less than two supports, but every team's experimented with both triple DPS and 2 tank 2 DPS on both offense and defense.
Which DPS heroes are most commonly used?
Every "offensive" hero sees a fair amount of use with the exception of Tracer. Reaper's definitely one of the most popular picks though at the moment.
Is lucio always used, no matter the map or situation?
Yep. Lucio's an extremely strong support. He:
- puts out a ton of DPS,
- has engage/disengage,
- has passive/active healing,
- has a multi-purpose ult
- most durable support by far
- has the highest skill cap of any support by far
Is lucio-zenyatta the most common and or best support setup? If so, in which scenario would you use mercy rather than zenyatta? Symmetra?
It was a common pairing in the tournament today, but "best" is a term that's impossible to apply in this context.
Mercy's value over another support is almost entirely in her ult (res), and on payload maps it's less about the specific situation (most of the time) than it is how the team wants to approach fights in general. With a Mercy on your team you want to fight, blow as many enemy ults as you can, die together, and hopefully get good res off. This is a lot harder to do now though because Mercy's res range was nerfed (40 -> 15 yards) and the ability to fly to teammate's dead bodies was also removed.
Symmetra's viable on the defense of the first point, but I don't see her being very useful past that.
Is reinhardt the tank primarily used/always used? Which others are seen in the current meta?
Reinhardt isn't used nearly as much as he was before (always), but is definitely still played. The tournament today showcased the power of double Wistons with double shields. Zarya's seen a decent amount, Roadhog's played on occasion, but D.VA is notably absent in teams' lineups.
Do teams ever run two of the same heroes? If so, which ones do you most commonly see, and in what situations?
Double Lucio used to be one of the few cases, but double Reaper and double Winston was very popular today.
Double Lucio is generally never a bad pick just because of the strength of the hero.
Double Wiston and/or double Reaper has an insane amount of in-your-face fighting potential that can't be ignored. It doesn't seem like any team has come up with an answer yet without more-or-less mirroring the lineup.
Do you generally wait for a good portion of your team members to have their ults before pushing, or just use them as members of your team get them to try and gain smaller advantages in team fights, attempting to get the jump on the other team before they can get their ults?
This is a question that I can't really answer with other than "it depends" -- the right answer in one situation may be the wrong one in another.