Technically, it would be the strongest of all themes as it allowed zdps to solo GR150. As far as consistent power, it is probably one of the weakest themes.
Yup. Nothing special except stacking massacre bonus.
For most people, ya, pretty uninteresting. For fun, though, if you get a massacre bonus over 1000, a super strong Uber Diablo will appear and try to wreck your day. He is significantly stronger than T16 Diablo or T16 Uber portal Diablo.