If you use the frag missiles and hit 2 guys per template you've got 7 "shots", against 8 from a Dakka pred, how is that more?
Also If you use frag your
AP is worst than the pred, 4/6 against 4/4, and your
str is lower 5/4 against 5/7.
You can use the krak missle, but that wil only give you 4 shots against again 8. The
AP of one of your shots is one point better, as is its
str.
So overall, I have to disagree with you, but yeah it is a bit slow.