Paracelsus is super overlooked which is a shame, because after finishing his rank up, his 3rd skill increases a servant's NP Gain for 50% for 3 turns at max level. So basically combining his 3rd skill with his second one, that gives the whole party Arts buff you can have a solid Arts support.
With Tamamo, she gives you Arts buff with her 3rd skill and NP damage with her 1st skill after ranking it up. But to loop with her it's bit complex (IMO) because it requires a certain setup.
Most of the time when I seen somebody use Castoria+Tamamo setup, they would equip Tamamo with Kaleidoscope CE , then use Castoria's first skill to fill Tamamo and the damage dealer's NP gauge (If Tamamo's Kaleidoscope isn't on maximum level, since MLB Kaleidoscope gives the user 100% NP gauge while non level maxed Kaleidoscope gives 80%).
In first turn you use your damage dealer's NP first which usually clears it, then in second turn if RNG doesn't screw you, the idea is using your damage dealer's NP again but at least leaving one enemy out, so that it can allow for Tamamo to cast her NP that gives the whole party a NP gauge for the next wave and decreases the party's skill cooldown. And then finishing off the remaining enemy with your damage dealer, again if the card RNG doesn't screw you over, it usually requires at least one card from your damage dealer to finish the enemy off. Then, in final wave you cast your NP again and hope that card they give you are the damage dealer's.
One of the most successful setups with Tamamo is the Castoria+ Jeanne D' Archer + Tamamo, because Jeanne Archer's NP gain is insane and in some cases you don't even need to cast Tamamo's NP for that, because Tamamo's Art skill buff itself gives Jeanne Archer all the steroids.
You can also try looping with Nero Bride, who 1st skill increases your NP Gain, which at max level gives you 45% NP gain for 3 turns, but after strenghtening/skill rank up
it gives you both NP Gain and fills up your NP gauge for 30% at maximum level. /SPOILER]