Are there any good arts aoe servants?

Nitocris, Shiki saber, Mordred rider, Nero

Shuten Doji, if you have managed to get her, that is or if you have friends with her on their support list. Her NP gives the most debuffs in the game that stacks with her skills as well. Then you can use other AoE NPs after that defense debuff to clear hordes of enemies.

I like Helena for farming. She also comes with a team-wide +20% NP charge.
For F2P, I recently rediscovered Paracelsus. His damage output is low, but with his NP charge skill he can fire off his NP first turn and he has a team-wide arts buff as well.

Sabers: Nero, Void Shiki, d'Eon (but no damage NP)
Lancers: None Arts AoE
Archers: No Arts AoE NP, Emiya and Arjuna are Arts-based
Casters: Nursery Rhyme, Eli Halloween, da Vinci, Helena
Riders: Martha (Red NP but 3 Arts cards)
Assasins: Shuten-Douji
Berserkers: None Arts AoE Damage NP (Vlad III and Nightingale are Arts-based, but Vlad is ST and Nurse is Support)