White Valkyrie is a conundrum. On one hand I understand why she has to be worse than the others. I would be pissed if she was exactly the same but you could get her for free. That would seem like a real slap in the face to the other colors. On the other hand, it sucks that white just doesn't have a better option.
I mean, black had Vampire, but it still got a REM Valkyrie? Why does it get a farmable one and a premium one and white doesn't? Edit: Not to mention the heartbreakers of the other colors, which I briefly forgot about. Shut up, it's early. :p
The way I see it, there are two fixes for this, although it's probably too late for either of them. Either just give white two Valkyries, a farmable weaker one and a stronger REM one (although that would massively devalue the iconic monster that Rose is, which sucks) or just make her significantly different from the others. If she had awakenings that were completely different, being less obviously good but not straight-up worse either, she could justify her existence. Like maybe give her three or more orb enhances, or fully defensive awakenings with multiple jammer, poison, and blind resists. Anything to make her more than just "the shitty Valkyrie".