So, I ended up being tossed into the jaws of DPP DOU for 2 tiebreaker sets during VDL, and I'm going to share some thoughts and teams I had while building during that short period of time.
First of all, Mew is one of the best leads in the tier, and despite how much it's already used, I honestly think it could be seeing even more usage. If I was ever struggling to figure out what my lead should be, I usually just circled back to Stealth Rocks Mew. The value of Stealth Rock chip in DPP alone is enough for me to put it in Tier 2, and Mew is also one of the most reliable clickers of it imo. On top of that, it has access to a bunch of other viable sets like the offensive Life Orb/Expert Belt one (even though I'm not much of a fan of that) or something more niche, like the set I used against Jello pasted at the bottom. (Just ignore the part where Mew got sniped T1 by Specs Shadow Ball in the actual game)
Shifting focus to these two guys because I think it's pretty difficult to have one of the two on every team, some of mine even had both. I should preface this by saying, Metagross is a clear Tier 1 and Heatran falls a tier below that simply because Metagross is much more flexible, for example, being able to run Stealth Rocks lead, which I've already pointed out how important that is, not to mention it's not as worried about being sniped by like a stray Ground move. No need to echo what oops said about Metagross above, just going to add that there isn't a world where Metagross isn't top tier since it pressures a majority of the better choices (like Tyranitar and Latias and isn't hindered by Hitmontop either). While both can run Leftovers Substitute, Heatran is better at it, but either way, you make it pretty difficult for your opp to position into a more favorable board state otherwise you'll get a free sub off, and it takes good advantage especially of Toxic and Sand chip from the likes of Hitmontop or Zapdos and Tyranitar, respectively.
Now, I'm not crazy and won't go saying it isn't high tier, but I don't think it's quite
as good as people say. Don't get me wrong here, you're guaranteed insane value just by setting Sand as the importance of chip in DPP cannot be understated. However, offensively speaking I have seen it get farmed so hard because Metagross is everywhere, there are a good chunk of good Water-types, and Hitmontop is similarly everywhere. Now, Choice Scarf Tyranitar is slightly less of a victim of being a do-nothing, but still.
I'm getting kinda tired here, so I'm going to give the rest of my thoughts about the good mons in rapid fire. Oops is right about Raikou Screens in his post above, but I still think it makes games very intuitive planning-wise to just set screens (and maybe rocks) off lead, then use that to set up and should not be discounted despite the flaws with chip damage (plus, it's especially good against comps like rain). Suicune is probably the best setup in my eyes, as long as you have some way to keep Toxic in check (e.g. Heal Bell) because it not only does its job being bulky, but Zapdos is the only top tier threat that can farm it; plus, Icy Wind helps its partners to safely make progress as well. Not much to say about Zapdos, it's very good and right up there with Metagross, Mew, and Latias in my mind, but perhaps Toxic+Roost should be taken more advantage of, matter of fact, Toxic stalling type stuff in general should be used more. Scizor is actually a little better in practice than I thought it would be in a meta with a good number of things it doesn't threaten at all; I had success with Choice Scarf Scizor lead (even though leading it is basically annoucing it's Scarfed), and setup fits well on Screens and Rain, as it threatens what it needs to and leaves the rest to its team, simply put. Next, I'm not much of a fan of Gyarados as the setup choice; Special setups are always preferred, and I think Gyarados is just a slightly worse choice than Suicune because Hitmontop just cycles in and out on it, plus Zapdos threatens it even more (and if you do manage to get +1 in front of it, you have to rely on Stone Edge!). It's also not good against Latias and you will get Toxic stalled. Finally, Swampert should be used slightly more, nothing more to add.
Lastly, my opinion on fullroom is that it's not very good. Why? The perk it has is that Bronzong and Cresselia are bulky and great setters, but the issue I have with it is how linear it plays and how exploitable/mid the sweepers are. Literally, a majority of the time I've seen Trick Room it's just Rhyperior dies without getting enough value -> you lose. I tried working on TR with a Suicune or Gyarados setup mode, but it wasn't working out, though it had merit.
Now for the teams that I used/planned on using for VDL tiebreaks:
G1 vs Jello
:Metagross: :Mew: :Heatran: :Zapdos: :Latias: :Hitmontop: This team is imbued with a couple of techs that help it against Rain, most clearly the Sunny Day Hitmontop and Lum Berry Metagross for Wisp Gengar (though, it was originally Metal Coat). Also, not to get sidetracked here, but I saw a couple of Adamant Attack invested Hitmontop from teams released in this thread and let me just say that you're 100% wrong there; run bulky Careful, so it actually does its job properly. Anyway, it also has Soft Boiled on the Mew and Toxic+Roost on Zapdos, among other things like Sub Heatran to help with stalling antics.
G3 vs Jello
:Raikou: :Mew: :Heatran: :Scizor: :Latias: :Suicune: Unfortunately, I did not get to use this one, nor did I get to use my other Raikou team :(. However, the idea is pretty simple: set up Screens and Rocks, then set up with Scizor or Suicune. I forgot where I saw it, but I remember Icy Wind Toxic Latias being pretty cool, and that was my idea of dealing with Zapdos and opposing Gyarados/Suicune.
G1 vs Actuarily
:Mew: :Scizor: :Heatran: :Kingdra: :Tyranitar: :Zapdos:This was heavily influenced by the goats Akhant and oops, as I wanted to try out Scarf Scizor lead (but uhhh, originally, I forgot to make Scizor faster than Scarf Tyranitar, which almost lost me the game--I fixed it now). Then, in my tests with Akhant he had like Shuca Berry Heatran multiple times, so I was like sure, I wanted to change things up a bit and not gamble on Heatran speed ties or be scared about Metagross EQ; it has HP Electric for Gyarados. Scarf Kingdra is a very solid cleaner and gives assurance against Rain, so I think it should be used more.
G2 vs Actuarily
:Latias: :Metagross: :Hitmontop: :Salamence: :Suicune: :Celebi: Pretty simple Suicune setup that utilizes Lorb Latias and CB Salamence as wallbreakers. Mence does struggle a little bit, but Icy Wind Suicune helps it out a little bit in terms of things like Latias and Ice Beam Mew. The star of the show is Celebi, with Heal Bell to counter Toxic for Suicune, outspeeding Heatran and threatening with EP, and threatening Scizor with HP Fire.
G3 vs Actuarily
:Raikou: :Latias: :Heatran: :Tyranitar: :Swampert: :Hitmontop: I didn't get to use it, but it's very simply just Screens+CM lead. I'm a fan of having the Rocks on Tyranitar even in the back, and then otherwise the team relies on Sand chip + Toxic chip.
To my own surprise, I actually had a lot of fun playing and building for DPP. I think it's in a pretty enjoyable spot, and I would honestly play in the future :)