So... Short story dots don't stack on the same target from multiple warlocks?
I was with another warlock in group, I was level 20 with level 14 skills learned, and he was level 22 with w/e skills learned.
We tested Agony and Immolate on the same target. My agony with 1/3 improved Agony got removed and I was unable to override it. Immolate as well.
Now curse or reckless as well doesn't remove fear as it should.
For example:
Use fear then use curse of reckless... Nope, target still runs in fear.
I don't know if this is an issue with spell ranks and if this issue is not applicable at max level. That's why I made this forum post so people could actually test this on multiple levels, and would be nice to report if this is true.
EDIT: So it seems that it's based on ranks. SInce my Immolate at the time of writting was rank 2 and agony rank 1. And his was rank 3 and rank 2 respectively... But it still counts as a bug.