Ryoma has some steep competition among AoE Arts Lancers: remember when Fionn was our only option?
When it comes to farming he loses on the refund side (he needs specific MCs to be able to loop standard 3-3-X nodes without Plutsuit), but his 50% charge, party support & ramping damage (best compatibility with Oberon among the other Arts Lancers) can make him the best choice for irregular nodes with multiple DPS or when a strong nuke is needed in room 3 (with Oberon again).
In Challenge Quests he definitely shines the most compared to his peers: his kit let him brush off the most annoying gimmicks in CQs (buff removal & debuffs), he pairs extremely well with Castoria (giving her NP extra overcharge) and his ramping damage is perfectly compatible with Oberon.
PS: Youtube is starting to block FGO videos in some countries, since Lasengle/Aniplex/Sony is spamming copyright claims for FGO soundtrack playing in background during gameplay. If you find some muted sections in my videos, that’s why… Not being able to upload pure FGO gameplay without changing the BGM is a bit of a pain really.