Exactly why crappy artis shouldn't be entered.

I dunno... There's some basis for having a less than stellar drop. Dark Arms Carriers drop what many people consider crappy... Krionite Torpedo. DACs are only one level up on spawn rate from the Experimenter. So having a "crappy" potential drop at a medium (50-60%) would be a balancing factor for some of the better drops.

What if they were made experimenter rarity, then the rarity would offset the rewards.

I just don't think the rarity would be sufficient to balance some very nice (limited for a reason) artifacts. A rare chance on a rare NPC sounds good to me considering the items obtainable could only previously be gained from spending a lot of energy and possibly artifacts on a mission. Remember that because spawns are determined by the RNG even the rarest of rare NPCs can just pop onto your BT when you log on.

I know believe me, how do you think I got the exotic mission by rank 200 with 2k kills?