I would like to share my thoughts, though probably a bit late here. I enjoyed playing Virtuoso, the cloneless concept is nice since the dagger stays with you even when mobs die. However, I couldn't shake the feeling that it's a bit... bland. I suppose it feels more of the same, I guess?
The two other elite specs seem to have a bit of "identity". Mirage offers a new evade system and thematically is illusion/deception on steroids. Chrono used to be the master of time (alac, slow, and quickness), tho now that's no longer true unfortunately. But Virtuoso? Seems to be some sort of bard-type theme, but do not feel like that at all.
Maybe the bladesong mechanics should be more about playing music? Eg throwing the dagger one at a time, but you can create some combo (chords/arpeggio) to create unique effects (eg, F1-F2-F3, or F4-F1-F1, etc). And perhaps the phantasms are your "orchestra members" which would react uniquely to each "chord" played during their appearances.