I wouldn't particularly increase the points cost of either of them, just to get them on the field more often. Good ideas all round though
For Sauron, I like the 3" knock back and knock to the ground, could be devastating to heroes though. Ancient Evil being -2 is good on both models. To be honest I'd be interested in seeing it as a -1 but making it add up with the others. The others should have a smaller range so could still work ok.
He shouldn't be a monster, he doesn't need it, he has might. The Balrog has no might therefore needed it. Its just too much to give him all those options, if you mix it with a taskmaster and manage some decent rolls, there is no way people could stand up to him. Channelled chill soul followed by possbile free heroic combat followed by hurl.. you're looking at 10 dead models in 1 turn.. from 1 guy even if his is the biggest bad guy.
The Balrog, why did you increase it by so much? Leave the cost the same, he's not very usable as is. I don't like crushing blow, he is rarely going to win with it so I doubt people would even use it. The other things I like though. Just the flaming aura and ancient terror would be sufficient.