Just to confirm
Hard mode with 3 people

Normal? Hard? Hell? Also, your screenshot shows 2 people, not 3. Does anything other than bosses even spawn with only 2-3 players? How long did you farm? And looking at how far up in your chatbox you scrolled, how can we know for certain this wasn't the results of a grind 10 minutes earlier and you then just joined a party?

As much as I'd like to believe this, I've only heard of 2 cases where orange glass marbles drop in a party and those players haven't been able to reproduce it. You've also provided somewhat inadequate information. If you intended to prove orange glass drops in a party, why did you not screenshot it on the ground of the dungeon rather than in chat box? Was it simply an accident?

P.S. I'm quite skeptical of everything as you can see.

Chatbar scrolled up. Must be hiding something.
2 players. Other 3 must have left.
No exp messages. Must be normal.

Looks fake. *flies away*

It's presumably Normal difficulty, since the enemies are level 7. Can't tell if 2 or 3 members.