Well, I got the party rolling but I have the stats to dual to most specialists, so I have some time to think about it. Playing HoF with beginner characters is a great way to cure yourself of the urge to start over.
If you dual a F/M at a high enough level, you hardly notice the drop-off in Thaco.
After a certain point it doesn't really matter, especially when combined with the melee power of grandmastery.