Well, to maybe give something to talk about, I'll post my current magicite teams in case it gives anyone some ideas. I haven't been recording magicite kills lately, but if a video of any of these teams in action would help someone let me know and I'd be glad to upload a kill video. In these lists, I'll point out units that are not legend dived, but unless specifically noted, everyone else is fully legend dived.
Maliris -- about 23 second kill on average
Tidus -- sapphire shot, lifesiphon -- CSB, BSB2
Bartz -- engulfing quadstrike, lifesiphon -- USB
Shelke -- entrust, wrath -- no SB
Onion -- entrust, wrath -- pUSB
Yshtola -- curada, shellga -- BSB
This team spends the first two rounds using lifesiphon/wrath to build up some soulgauge, then I water chain with tidus, usb with bartz, then feed tidus lots of soulgauge for him to spam his bsb2 every round. Water is one of my strongest elements so this one is an easy 23 sec or so clear.
Isgebind -- 28 seconds on average
Locke -- ruby spark, thiefs revenge -- CSB -- not dived
Yda -- fires within, lifesiphon -- USB -- not dived
Bartz -- flaming quadstrike, lifesiphon -- USB
Onion -- ultra cure, affliction break -- pUSB
Yshtola -- curada, protectga -- BSB
This team barely squeaks out a sub-30 win, but it does manage to sub-30 him reliably. Bartz uses a bow while Locke and Yda use fire skills that are innately ranged so the air phases aren't a problem. If I were to legend dive Yda I'm sure I could drop my kill time somewhat, but this team does it fast enough so I haven't bothered.
Tiamat -- 55 or so seconds, my worst magicite
Onion -- wrath, entrust -- pUSB
Alphinaud -- curaja, protectga -- SSB (radiant shield)
Arc -- curada, shellga -- SSB (instant pBlink medica) -- not dived
Relm -- ultra cure -- BSB (last stand) -- not dived
Squall -- snowspell strike -- BSB2
I haven't fought Tiamat in months. I farmed him 4 times to get a level 99 Tiamat magicite but haven't been back since. This team works, but it's painful and my options for ice are horrible (other than OP squall). I have to go back and farm more magicites from him soon, but I'm not looking forward to it.
Midgardsormr -- 29-36 seconds, depending on dualcasts
Ramza -- wrath, affliction break -- USB
Onion -- meltdown, gust -- mUSB
Fujin -- raging storm -- BSB -- not dived
Alphinaud -- tiamat, protectga -- BSB
Sarah -- curada, shellga -- BSB -- not dived
I feel like I can improve this team some, but I haven't done him in a while so I haven't spent much time playing with the setup. This works, but it's kind of RNG since I need to dualcast a lot to skip some scripted attacks otherwise it can get kind of dicey.
Ixion -- 26 seconds on average
Onion -- chain stonega, wrath -- mUSB
Aphmau -- curada, protectga -- USB -- not dived
Arc -- ultra cure, shellga -- SSB -- not dived
Maria -- meltdown -- BSB
Alphinaud -- titan -- BSB
Ixion.... you're either easy or a complete pain in the ass that requires a reset. It's just a big pile of RNG. If he uses his aoe dispel too soon, it's a reset. If he waits a few rounds until I have Onion or Aphmau soulbreaks ready to re-apply haste before he dispels it's an easy sub-30. Not hard, but very tedious.
Kraken -- 21-25 seconds or so
Shelke -- wrath, entrust -- no SB
Lightning -- thundering quadstrike, lifesiphon -- USB, ASB, BSB2
Kain -- cyclone bolt, lightning dive -- CSB
Onion -- ultra cure, protectga -- pUSB
Yshtola -- curada, shellga -- BSB
This fight used to be one of the harder ones, until I got a fully geared Lightning from last festival, and now it's my easiest farm. I spend 2 rounds lifesiphon / wrathing up some soulgauge, then Kain drops the thunder chain, Shelke starts feeding Lightning a bunch of soulgauge, and she just lets loose a world of hurt by spamming usb bsb2 usb usb ASB and Kraken melts extremely fast.
Siren -- 27 seconds on average
Shelke -- wrath, entrust -- no SB
Onion -- wrath, entrust -- pUSB
Orlandeau -- dread weapon, banishing strike -- OSB, BSB
Shadow -- ancestral reflection, shadow embodied -- BSB
Yshtola -- curada, shellga -- BSB
This one feels a bit gimmicky, but it works for a reliable sub-30 every kill. I use Orlandeau to OSB early on to give himself the cast speed buff, he uses banish strike to remove Siren's first haste/regen, then he just spams his BSB for the damage on entry with Shelke feeding him soulgauge. Shadow does some support damage with dark ninja stuff. It works, and since most of the damage is from soulbreaks the counter-curaja in phase 3 isn't really a problem.
Hades -- 40 seconds on average
Orlandeau -- assault saber, lifesiphon -- OSB
Onion -- ultra cure, protectga -- pUSB
Marche -- guardbringer, divine cross -- USB
Iris -- curada, shellga -- BSB -- not dived
Larsa -- wrath -- BSB -- not dived
This one I can't really sub-30 with the team I use, but it works to reliably clear Hades every time. Larsa spends the whole fight wrathing into his BSB for astra at key times, while Iris helps with her BSB that also does astra so I never get a single status effect applied. Orlandeau/Marche do the damage. I think if Orlandeau had his USB instead of relying on his OSB I could sub-30 this, but I don't have it....
Sorry for the wall of text!