My view on breakpoint: it's a non-issue for mage bomb, especially since LB will be fixed to scale linearly too. But it's a big concern as fire for Pyro and Combustion as they aren't chained and the number of tick have to maximised.
For proc, it's easy : the bomb's DPET is by far superior to any other spell, what ever breakpoint you use. And proc have a 15s duration.
@kuny : good news !!!