I'm conflicted...
On one hand, the stories are journeying too far into the deep end of magical society for a simple mortal to hold their own. We can argue about Valmont's "It's how smart you are" remark all we want. But... well, there's a certain point where a mortal needs to resort to remote controlled weaponry, or heavy vehicles instead of a few guns and gadgets.
I don't see Valkyrie in Murphy's future. WoJ also said that Murphy wouldn't get any power ups so I think it's fair to say she'll probably stay vanilla human. However, I don't think there's no place for her by staying that way, especially since she's repeatedly shown her abilities to adapt throughout the series. Even in GS, a large part of what she was doing there was managing people and organizing - those are pretty essential skills.
I know JB has said that...but I don't know that he'll be able to keep it.
As Smaug notes, Karrin's role in the story is start to strain a bit. She isn't precisely a liability to Harry in emergencies, but at the same time, things are becoming such that she's not as much of an asset as she once was, either. Her skills are useful but she's freaking
fragile.
That's no put-down of Karrin. But without some kind of power up, or something, the point is coming where it's going be very hard to see what her
function in the story is. Is she Harry's backup in tight situations? Well, she can do that, to a degree...but Molly can do it as well or better now. I keep thinking about when Harry went into Marcone's office to present the weregild, back by Molly. She was utterly natural in that role...and she can wield serious magic. (That's aside from being WL.)
(I could see a weird jokey dynamic emerging with them, Harry and Molly deciding if in a given situation they're about to be the Winter Lady backed up by her Winter Knight, or Wizard Harry Dresden backed up by his faithful sidekick Wizard Molly Carpenter.
"OK, so we have to confront Mother Winter about this," Harry said. "I'll back you up.'
"It wouldn't be appropriate for the Lady and the Knight to do such a thing," Molly said. "So Wizard Dresden had better do it. I'll be right behind you."
"The Merlin would throw a fit if we involve Council Wizards in Mother Winter's business," Harry countered. "This is Sidhe business. But I'll back you all the way!"
"You wouldn't send a helpless girl to face Mother Winter?" Molly asked, suddenly sounding remarkably delicate and frail.
"Never!" Harry averred. "Luckily you're the Winter Lady instead of a helpless girl."
"You've been hanging around Marcone too much," Molly grumbled, sounding like herself again. "You're getting sensible." )
Is Karrin his contact with the mortal law? Well, not exactly, not anymore, and events are moving in directions where Harry's contacts need to be higher level than Chicago PD anyway. Harry needs some FBI contacts, maybe some Scotland Yard contacts, etc. CIA and SVR wouldn't hurt, either.
Is she the head of the Chicago Alliance? Well, she sort of is, as much as anybody is, but it's not clear that this is that big a deal at the levels Harry now moves on. Sort of like being head of the Paranet. A useful contact, but still....
Karrin gets hurt in
Skin Game, so she doesn't get to go on the mission. But what exactly would she had contributed if she had? That's a serious question, not a put down of Karrin. That mission needed major backup, and JB ended up giving Harry Sir Michael and Goodman, both of whom can do far more than Karrin can.
I don't know what JB has in mind, but I don't see Karrin's role in the story continuing as it's been for much longer. I'm not sure how it can work.