It finally dropped, so it does still exist from this named. I'd say I spawned Cawrolis about 17 times over four days of 14 hour-each sessions. I got three robes, rest were sheilds, and finally, the Bowl of Bone Dust.
This doesn't mean the Bowl couldn't drop faster, or slower, But it is a very rare drop. I camped for this before ( a long time ago), but I gave up too soon. I was about to give up again.
Needless to say, I will never sell it (It's priceless to me).