if i may ask, how exaclty does one execute the "infinite combo exploit"? asking for a friend
Break both guards at the same time, lift them once, use Piercing Edge (the skill that stabs 4 times) in a way that you can hit both Hobgoblins at the same time. You will recharge more AP than the amount you spent and you can spam this a lot, I took half of their hp with this tactic (you can have them stay in the air until they hit the ceiling, after that they will slowly start to fall down). Blade Rondo is better, but you probably won't have that skill unlocked at this time, even piercing edge is a stretch, I unlocked that skill just before the end of the chapter.
A reliable way to do it is to use Lecia's ultimate, run around a bit and counter when they are staying in the same place.
You can fight this again in the arena, but at that point, you can kill them with an aerial combo without relying on the infinite trick with all the skills you have.
Flying Slice, Seraphix Cross, Blade Rondo, Tempest Roll, Lunar Assault, Crescent Step, Piercing Edge, normal hit (have the normal hit don't break the combo +1 ability) and Sylphic Dance.
Without that ability I mentioned, put Sylphic Dance after Lunar Assault.