comparing farming servants based on their CQ potential

You mentioned this, so my point is basically majority of the available servants are up for discussion.

This just makes for a weak discussion post. Why don't you start us off? For example, Merlin + Castoria + Morgan makes for a solid stall/DPS team for any CQ, but once there's buff removal the whole team falls apart, like for LB3's recollection quest.

Some CQs can benefit from solos, while most others require team planning and a strategic approach.

If you really want an answer, then Melusine's kit is one of the most stacked. Self NP charge, NP gain and star gen for NP spam, and/or Pierce Invincibility with a 100% NP charge for her AOE NP. Her weakness is the lack of critical buffs which can be helped with command codes, while buff removal will be another weakness, even if there is a CC with a 10% buff removal resistance chance.