Sometimes they are dead meat, most of the time actually, but when you can gear him up with a sword and whip make it worth while putting them in for me. Also people don't usually expect it, besides stealth events,
Armor is usually the most common way of negating the balrog, and the whip stops that. Sometimes they're prepared for a 17 strength rog, 20 strength has got the overwhelm for me a few times.
I have never tried a dedicated balrog deck in fotr.. Is it feasable with only two underground sites..?