This would have been my 'dream team' a few years ago.  I think 5 or so years ago, everyone's ages would have fit.

Harry Dresden - Eric Balfour (talk, dark, gloomy, seems to have a sense of humor, but can look dangerous)
Karin Murphy - Sienna Miller (tiny, but FIERCE!  well, tiny, but maybe too hot)
Bob - James Marsters (and why not? doesn't he deserve it?)
Thomas Raith - Justin Hartley  ( i think there is similar bone structure in the face between Eric & Justin, but Justin may be taller)
Michael Carpenter - Christopher Judge (so sue me, when I think of Michael, I think of Judge being patient, calm, and confident in faith)
Mab - Tricia Helfer (I picture her walking down the hall in a suit with Eric watching her leave... fine looking suit. hot but cruel? yes.)
Susan - Tamara Feldman (oh come on, it's not like anyone likes Susan, so why would they like the casting?)
Charity & Molly - really, they just need to be tall hot models, so take your pick.  But Molly has to look good in goth, too.
Ebenezer McCoy - Wilford Brimley (search your feelings, you know it to be true.)
Leah - Famke Janssen (redhead, hot, can be calm and cool, and then completely off her rocker?)
Donald Morgan - maybe Adam Baldwin (i think he could pull off grizzled vet, but maybe not old enough)
The White Council - Any number of Brits (like it really matters)
The Black Council - Any of the ringwraiths (well what else did you expect?)