like i said just leave the 11s alone and change normal ones so it possible to kill people with(even tho there are ones thats good to kill people with for me and tiggur at least). im not seeing much of a difference btwn 11s and 10s cuz whocares if someone has the 11s and cant aim properly. ALOT of donors just out tank people with the worst aim they could have, so i dont think its shotgunz problem. (it might make difference but still on my point donors are called donors for a reason, and people donate for them for a reason).
so my suggestion is keep 11, change store gunz delays to 1000 from lvl 1-40 41-70 make them have a range of 850-950, 71-90 800-850, 90-99 make one thats the same as the 11 dmgs as in the delay but 10 dmg, and the rest range from 750-800. since 11s are 700 and they are donor items, they need to be a bit better than the rest, and the donor shotties should have a 850 delay if ur changing the delay of shotties ingame