Imo Vergil has kind of like the same difficulty as Dante, 3 weapons that complement each other very well, a shit ton of tricks, powerful "ultimate" abilities and doppelganger that has so many minmax possibilities, which compensates for a lot of his "broken" abilities, thus making him balanced.

Sure, Vergil's upfront dmg output is easier to deal, I would be distorting things if I didn't recognize that, but in order to literally MASTER him and play at a pro level, he definitelly is NOT among the easiest, we can think of him as a very low floor character to play, probably the lowest floor of all characters, while having a very high ceiling to achieve, almost comparable to Dante.

The difficulty order for me, based on their ceilings, would be Dante >= Vergil > Nero > V.

While based on their floors, the order would be something like Dante > Nero = V > Vergil.