This is all I could find on it, I didn't see anything about luck still being able to effect it. On personal exp it took me about 3-4 loops around to get one to drop without luck. Haven't tried it with luck.
Publish 48b
Doom Creature Point System - Reduced the number of points each doom boss rewards.
Publish 48
Killing bosses in Doom will increase your chances of getting an artifact drop:
Each player character participating against a gauntlet boss or the Dark Father will accumulate artifact reward points.
The more artifact reward points a player character accumulates, the more likely an artifact will spawn in his/her backpack.
Player characters who score higher on the Top Attacker list will earn more points. However, everyone in the Top Attackers list that stays the entire duration of the combat (even if slain) will still earn points.