SS/Invul here. I am 25th and have had no problem soloing at all. Only time I really die is when im in groups more than 3. 3 is the lucky number it seems for me that I don;t have any problems.
As for powers. I have jab,punch,KO,rage,temp invul,dull pain, resist elements, flurry sprint, health,stamina
Most fun I have had with any toon in this game(coh as well)