Bosspoles, first and most important thing, get them.
Drop 1 grot, and you wont need 2x Runtherds, 3 Deff Dreads with Rokkit Launchas wont be able to hit the broadside of a barn, I´d either drop them in favour of more boys, or get something more hit-friendly, either flamers or CCW´s, but 3 is overkill, I´d stick with one or two.
KillaKans with Rokkit Launchas will hit the barn, but probably wont do much more than give it some holes, it´ll still be functional, s8 ap3 aint that usefull, even though you´ll hit, you can only glance AV 14, and its a dicey 50/50 for a glance, and even then a low chance of destruction.
I´d try to push in another squad of boys (dropping a deffdread), and dropping the third deffdread in favour of additional 3 kans.
Drop 1 grot, and you wont need 2x Runtherds, 3 Deff Dreads with Rokkit Launchas wont be able to hit the broadside of a barn, I´d either drop them in favour of more boys, or get something more hit-friendly, either flamers or CCW´s, but 3 is overkill, I´d stick with one or two.
KillaKans with Rokkit Launchas will hit the barn, but probably wont do much more than give it some holes, it´ll still be functional, s8 ap3 aint that usefull, even though you´ll hit, you can only glance AV 14, and its a dicey 50/50 for a glance, and even then a low chance of destruction.
I´d try to push in another squad of boys (dropping a deffdread), and dropping the third deffdread in favour of additional 3 kans.