Against escorts abeam at 30cm, FP18 would get 4 dice. This is unlikely to kill 1 escort even under current rules.
Against escorts closing at 30cm, FP18 would get 9 dice. For 5+ escorts, the breakdown is:
14.3% no kills
50.7% 1 kill
30.7% 2 kills
4.1% 3 kills
0.09% 4 kills.
Average 1.25 kills.
Splitting fire 4 dice vs 5 dice with no carry over, the breakdown for 4 dice is:
59.3% no kills
40.7% 1 kill
and 5 dice is:
46.1% no kills
53.9% 1 kill
average: 0.94 kills, but a leadership test is needed to even split fire. Assuming average leadership 7.5 (averaging the fail chances of ld8 and ld7), there's a 34.7% chance fire won't be split, in which case you'll expect 0.86 kills. The total average would therefore be 0.915 kills, a 26.8% reduction in effectiveness.
Splitting fire with 3 dice at 3 targets and no spill over, the breakdown is:
74% no kills
26% 1 kill
x3
average: 0.78 kills, which is worse than firing at 1 target, so why would you?
As I said earlier, this is a significant buff to escorts.