Wanted Ophelia got Silas instead, is this a good build for him

his res already so low and you got a bane which is even worse for berkuts lance. You want plus res or neutral res with berkuts lance. U can give him brave lance if you want

I don't think you should go for the Resistance refinement for Berkut's Lance. Yes, Silas can handle dragons more easily but he's still quite slow. He will probably benefit more from a Defense refine to make him a cavalry Lukas, essentially.
Or you can remove Berkut's Lance completely, and go for Slaying Lance, Brave Lance, etc. instead.

Maybe go for a normal bulk build.

Try using a -spd +res Silas after demotion for this build.

Way too much investment for a build that you’re not even confident about.

I'm surprised how little credit people are giving you.
48 def 41 res on enemy phase when def wave is not active. Yes, the res bane isn't ideal, so if you make this build switch to some -spd or -HP if you can. But even with -res it's not to sneeze at.

Not a big deal getting doubled by manaketes, although it might be preferable to avoid it if possible (or maybe not, because you might want the bonfire for blasting through their def). Most manaketes don't have that high of atk, the two most notable exceptions being BoF A.Tiki, who is colour disadvantaged against him, and M.Grima, who he probably shouldn't be fighting.