Oh my, are my lurker days virtually (allmost pun, intended) over 
I think Cool Beats is completely viable in NM!
Paint all the targets in a group, once. The little sky blue numbers will litter the screen. Follow up with one Power Chord and you are off to the next zone. It should be used like a jab in boxing, it softens up the opponent for your big punch, or for that crappy Reaver running around. Whatever. It's dead.
Depends on stats, heavily, needs heavy stats
Then there is the possibility that I'm not just good enough, but I'd rather blame stats 
For me virtuoso + Cool Beats is pretty much only mage I can solo trough perilous in reasonable time scale, eg. making 30-70 kill killstreaks. Tactic is simply running faster than enemy, giving extra armor to self only when under heavy fire from ranged units and giving Cool Beats, preferably to small groups at the same time. Keeps nicely mana flowing and kill streak growing. Just started to run with enhanced CB ring (finally 10% HoK is enough with this style) and have to go with Heart of Despair for smaller damage just in case I get company and cant keep running any more. Cant even dream doing same in NM yet 
New players mess this style pretty fast. I allways try to adapt my play style to group, but it takes time to find out who needs whitch buff and what works best for whole. People running away from virtuoso who is trying to give more speed and armor doesn't help. As said earlier, they probaply don't know what virtuoso is trying to do, and any way if you don't stay alive with extra 170 or so armor in perilous, maybe, just maybe, you should play few more threatening and/or craft better armor
And players with high stats mess this even more making sure I dont get mana enough because they kill everything before me 
That said, from mages I enjoy most playing virtuoso and don't mind playing it also solo. When speed running virtuoso is good company.
I learned just few posts earlier about power chord not generating free song if done too fast, and this bit of information might alter my virtuoso style, who knows, I might become usefull most of the time...