That's an interesting change, but I'm not sure overall. You know I get Original Blue, so we'll leave that aside, but the new team seems like it mixes too many concepts. What I mean is: Khorvash is a good tank and does true damage, plus mana drain. Rowanne does split damage, but doesn't have anyone to buff her armor. Valk feeds all three and no mana blocking, so same as OB. Mab freezes and does mana burn (but not good against impervious if I understand correctly).
In my mind, the real value of OB is that it (because of Shadow Hunter) quickly eliminates one or more troops from the opponent deck (cutting one or two legs off the table). Your new lineup looks like it would gradually whittle down all four. On the flip side, you do have mana drain and winter veil, while OB doesn't do anything other than damage, so that's the part that I'm not sure about.
With no one to buff Rowanne's armor, why would you drop her in in place of Druid?