I wouldn't say that magic is nerfed in this game (unless you are talking about Nosferatu), but most of the magic users you get are mediocre.
In Birthright, Orochi is slow and very fragile, and Hayato comes way underleveled with terrible bases.
In Conquest, Odin has low-ish bases and only average growths, while Nyx is made of glass and has problems hitting. Ophelia's paralogue does give you good things like Horse Spirit and a Reverse Spirit, though.
In Revelation, Hayato is much better for he comes with reasonable bases and makes a good Oni Chieftan. Orochi is mostly the same as in Birthright, but joins later which makes her even worse. Nyx and Odin come very late in Revelation with terrible bases and are ORKO'd in their join chapters. Felicia can be sealed into Strategist in all routes, but she's also frail and has to deal with E rank tomes for awhile.
Depending on your difficulty, the only units I would call unsalvageable are Odin and Nyx in Revelation, but the only one that I would call good is Hayato in Revelation.