I have a 35th lev Energy/Ice blaster, I think Nova is anything but over powered. I use it and am left with no end, and usually mobs leftover (I have it six slotted by the way 1 accuracy 5 damage SOs).
In the manticore taskforce I was killed 3 out of five times using it.
If the damage of nova is lessened and mob hit points increased, well guess it's respec time.
Nova will be a waste of a power, just my 2 cents.