Just finished off the postgame campaign with the team I posted earlier. I, unfortunately, found myself more disappointed than I thought I'd be by some of them, although they still all pulled their weight in the end.
Decidueye (nicknamed "hanzo main") was one of my team's carriers since, well, it's a starter. No matter the time, I could always count on Decidueye to slap whatever was in front of it hard. Regrettably, its partial Ghost typing, which didn't bother me much initially, did hold it back quite a bit starting mid-game considering the abundance of Ghost-killers. Despite this, I really liked Decidueye through all stages of its life and I'll probably find myself coming back to it in a later playthrough.
Vikavolt (nicknamed "Road Roach") was a mon that I kind of expected to disappoint me for the obvious reasons that it doesn't evolve until the end, it switches attacking stats when it does, and its movepool is pretty shallow. However, it remained surprisingly useful as an Eviolite Charjabug and even came packaged with a Special Attack boosting nature, which made it a godlike Special nuke when the time finally came. Even if raising it gave me my fair share of grief, I'm still glad I chose to pick up a Grubbin on Route 1.
Wishiwashi (nicknamed "GET SCHOOLED") served as my team's main carrier, one-shotting even some mons that resisted its STAB with ease. RestTalk Washi turned out to be a bit more overpowered than I'd bargained for, and its godlike experience group coupled with the power of the Exp. Share meant that it was always 1-2 levels above all my other mons at any given time. This quickly made it my least favorite party member, which sucks because I really like Wishiwashi. Although it's one of my favorite new mons, I don't really see myself using Wishiwashi in a future run (except maybe for a SoloWashi run, which I've considered).
Dugtrio (nicknamed "Wiglett") was a mon that I picked up solely for its godly design, and it managed to carve out a solid niche on the team for its ability to outspeed everything (bar Hau's Alolan Raichu, that bastard...). Its typing, however, didn't do it as many favors as I hoped it would since it can't switch into anything running EQ (which is a lot of things) and still can't take hits worth a hill of Pokebeans, but STAB Iron Head was pretty nice for dealing with Fairies. I was kind of hoping to get one with Tangled Hair, but considering it's just a reskin of Gooey, I didn't bother SRing for it. All in all, this mon didn't really wow me, but I would consider using it again.
Muk (nicknamed "Da Huuuuudge"; shoutouts to anyone who gets the reference), on the other hand, wholeheartedly surprised me. Even if I couldn't find one with Poison Touch for the life of me, Muk's ability to eat damage from any source just astonished me. Since I found one with Black Sludge, I actually ran a pretty unique wall set with Infestation and Disable, whittling the opponents health down with chip damage and disabling their most powerful move before healing up and going for the killing blow. For a last minute addition, Muk most certainly allowed me to play the game in a new, less hyper-offensive way and was one of my team's most valuable assets.
Minior (nicknamed "smolrock"), much like Muk, caught me off guard with just how effective it was. I ended up running an offensive Shell Smash set, which pretty much let it one-shot anything--yes, even the Totem Pokemon--that was put it front of it. Most often, though, unboosted STAB Acrobatics would be good enough to get the job done on its own. Rock/Flying/Fairy provided surprisingly good coverage on one mon and also made Minior into my resident Dragon slayer. Overall, I absolutely love Minior, although Shell Smash did make the game a bit easy.
For a while, this was my team... until I found a Shiny Beldum, which I nicknamed Grossberg after all my other Metagross. Metagross is my favorite Pokemon and also has my favorite shiny by far, so I knew that as soon as I hit the postgame, I had to break my teambuilding tenants just this once and use it on my team. So I finished the game, swapped Wishiwashi out for it, and took it along for the postgame. Now, as a Metagross, it's a part of my team that I take into the Battle Tree with Muk and Minior, and I couldn't be happier with it as my first non-event shiny.