I would suggest mixing your set, but check the lofts on the different sets. I know the titleist 695 set differ up to 3 degrees from each other. I dont think mizuno differs as much, but check.
I hit the Yes! Sophia model (rear shafted blade). I absolutley love it. Not a fan of the grip, but that was easy to fix. I use the Pingman grip now, love it. No cons on the putter, great feel and rolls the ball well.
This may sound wierd but tee the ball higher. It will make you sweep the ball off the tee instead of hitting down on it. That should take some spin off.
I would definitely say that Adam Scott is now the best player w/o. I have to say though I was beginning to like Sergio until he made those stupid comments at the end of the British. However, I do think Adam scott has the talent, and...
In your case, I wouldn't say you need a 3 wood. Sine you hit the heavenwood like a fairway metal, you already have what you need. I think your set is just fine.