Shadowmourn and the fucking shards

Due to me beeing curious on the amount of shards that should drop in one icc 25 hc run, i went and did this:

Ive based the numbers on 75% drop chance from each boss ( since armory states 50-99% ).

So we have 12 bosses. n= 12
and each has a 75% chance of dropping a shard. p = 0.75
Binomial distribution of the dataz - P(X = k)=

This results in
P(0)=1/16777216 = 0,0000006%
P(1)=9/4194304 = 0,00021%
P(2)=0,0035%
P(3)=0,035%
P(4)=0,24%
P(5)=1,1%
P(6)=4%
P(7)=10,3%
P(8)=19,4%
P(9)=25,8%
P(10)=23,2%
P(11)=12,7%
P(12)=3,16%

We can further interpret this => theres a 91,4% chance to get 7-11 shards in one run.

Fucking shards, y u no drop in stacks of 5?