Are Raven tomes still viable?

Ravens are definitely still viable but Soren's shiny new Winds Brand, once refined, is better for him. Raven will always be useful arena and arena assault for Brave Lyn and, for greens with TA, Reinhardt. I run all mine (M!Robin, Lilina, Cecilia, Inigo) with TA and Bowbreaker purely for Lyn and they get frequent use in AA.

I just got another Spring Kagerou and gave my refined Wind's Brand Soren Spd/Res Bond. He already had Chill Spd. He's very unique and fun if you're willing/able to invest, and there are far better green raven users than him.

In higher arena tiers I tend to say no because most lyns use Firesweep Cancel Affinity anyway and not many other colorless units are around. Maybe that changes with Robin, but she has CA anyway

Boey runs a Raven tome way better than Soren, and he's just as easy to get. Keep Soren's wind brand and invest in a +def Boey instead. :D