Spamming Sewers for Fragments

I decided to check if there is a way to get fragments this way.

So i spam with parties of 4 (exact number) members.
All members have no items to break.
Periodically i do 1 update to inn (to get permanent speed up).

I decided to use big numbers (statistics loves them )
Only full success party raids are counted (anyone wounded - i skip that)
Right now the full picture is as follows:

Misses (no fragment seen): 269
Misses (fragment seen, but not selected): 25
Got it (fragment seen, selected): 6
Special: +2 fragment from bags (33 opened).

Total: 300 parties sent, 6 fragments.

So right now the answer is - NO, NO WAY THROUGH SEWERS .