So as I stated in the OP, I am going to share my party info
Party:
(front row)
P4 MC (Yu Narukami), Personas: Izanagi-no-Okami/Magatsu-Izanagi (DLC)
P3 MC (Minato Arisato), Personas: Messiah/Thanatos (DLC)
Shinjiro Aragaki, Personas: Castor/Yoshitsune
(back row)
Naoto Shirogane, Personas: Yamato Takeru/Helel
Yukiko Amagi, Personas: Amaterasu/Tzitzimitl
When encountering a Fast Guy, try not to enter the FOEs line of sight or it will chase you. Your best shot is coming up behind/to the side of the Fast Guy to gain the Player Advance condition. Or another unique condition appears when you are carrying the Holy Flame, the Fast Guy might panic during the battle costing it its complete turn.
The Setup:
for turn 01 you need to setup up for your attack next turn. I have the P4 MC use Heat Riser on himself to boost all his stats, next I have the P3 MC use Debilitate to lower the stats of the Fast Guy, then I have Shinjiro use Marakunda to lower the defense even further. Next the first attacks will be by Naoto using Mazionga and Yukiko using Agidyne (which gains the Boost state for weakness).
when turn 02 starts, the attacks all come out. Use your Leader Skill, Spotlight, to allow the P3 MC to attack first with Flame Link, then have the P4 MC use Raijinzan, have Shinjiro use Hassou Tobi (Yoshitsune's Heroic Gemini may kick in for a double Hassou Tobi). After words have Naoto attack normally and finally have Yukiko use Agidyne again (once the P3 MC uses Flame Link, every attack after it will link causing more fire damage to the FOE). If you are lucky, one of your party members will request for an All-Out Attack, use it.
There is a rare chance the FOE will survive the barrage, so use the same strategy in turn 02.