I'd like to contribute as well.
I know many people have problems with Gladii packs. A quick and easy way to wipe them out with Dante is to get really close to them while they're rotating preparing to attack, and use the shotgun. They will die with only one shot this way. Use Trickster to avoid attacks and to get close to them quickly.
With Nero, best way is to grab one and lock on to another. Nero will throw the Gladius to the one you locked on and they will both get destroyed. Also, you can DT and grab one in DT, Nero will swing it around before throwing it, damaging and potentially destroying the Gladii (or any other enemy) close enough.