So your assumption about weaker groups is wrong. If weaker group is not able to do full instance they will not unlock the artifacts and there is no point for them to farm anything.
I think there is a big misunderstanding: The loot that has been removed as a hotfix to remove the possibility to skip the content is returned to the monsters, so you will still be able to farm the normal artefact. For the refined one though, you will need to finish the instance. The content that is in the game right now will be retained, it's farmability even reverted to when it was first released, but it's improved counterpart will be locked behind the endboss.
Kalin is supposed to be hard, something to give the playerbase something to strive for. Weaker groups are not supposed to be able to clear the instance. These groups should otherwise try to find ways to improve.
You guys are saying that the normal version is meant for weaker groups. You also say weaker groups shouldn't clean the instance so they shouldn't have acess to the normal version of the item. Clear your mind please xD.
Instance is harder now than it was before. B1 removed possibility to kite. Locatha not dying at 50% means many groups can't kill it, etc. I think if you really wanna make normal artefact to be used by weaker groups, then activate the npc without needing last boss so those people can still farm the simpler version of the artefact.