Most darkfriends are really in it for themselves, expecting the Dark One to reward them for their service, rather than wanting to free the Dark One for its own sake. Most of them have not realized that if the DO actually wins they will be collateral damage in the destruction of the entire world. Thus, the DO may want balefire used without restraint but most of his followers would not be willing to use it to the required extent. If he pushes for it he might get a mass darkfriend revolt instead, and he's smart enough to realize this. Ishamael would go along with balefiring the Pattern to tatters, but he's just one person. He might be able to pull it off with the Choedan Kal, but with anything short of that he'd face a universal mutiny before reaching the point of no return.
The DO may or may not want the world torn apart by excessive balefire use. I don't think there is enough evidence to decide this either way yet.
I'm going to have to respectfully disagree with you on this one. Some of the most powerful people ever, the Forsaken, do whatever he tells them. If he told them to balefire the world into oblivion they most definately would obey. As would any Forsaken underlings. The DO rules out of fear as do the Forsaken over their cronies. If anyone disobeys they are simply killed off. That goes all the way down the chain of command on the side of the shadow. I don't see any type of revolt taking place. Furthermore, the Darkfriends that matter in this discussion are Aes Sedai Black Ajah and any rogue Ashaman that have crossed over. All of the Black Ajah are fully aware of what the DO represents. It's not just some shmuck darkfriends that would come into play in this theory only the channelers.
So, I still believe that if the DO intended the world be ended by excessive balefire use then that would have, at the very least, already have been attempted.
A lot of other people have answered this, but I would like to address this carefully and with full context.
Firstly, the Forsaken do *not* do whatever the DO tells them to do
if they think they can get away with not doing it. Think of Lanfear. She fully intended to rebel against both the Creator and the DO, given the chance. The other forsaken aren't quite crazy enough to think that that's possible, but Mesaana, for instance, thought she could ignore the call to fight at Shadar Logoth. She got punished for it, but please note that
she didn't do it. The obedience of the forsaken is not absolute.
Secondly, the Dark One does not rule strictly out of fear. As others have noted, he also rules out of greed and desire for petty revenge. Carrot and stick. Selfishness, in fact, is one of the prime motivators behind most of the Forsaken, as noted by Verin. Even in tGS, we have Moridin promising Graendel a high position of authority, and it works. There are too many other examples to count. I would say that, on balance however, that most people who serve the DO have greed for motivations. Lots of people fear the DO, and with good reason. Active service seems to come mostly from greed.
I would also note that disobedience is not strictly rewarded by death. That is false, period. Mesaana, Moghedien, and Lanfear are all examples of that.
Given these reasons, it seems perfectly logical that the DO is simply lying to the Forsaken, leading them on with promises of power and glory, until he can destroy the world entirely. Ishamael practically says as much to Rand, in fact, in their little meeting. The fact that the DO has not commanded the Forsaken to use Balefire may simply be because that would tip his hand; because he is motivating his minions with greed, they will revolt---they really will---if they truly understand what is happening, Ishamael excepted. I see no reason to doubt that.
Edit: I would like to add that it seems logical that just anybody using Balefire may not be enough for the DO to get everything he wants. It does seem logical that having Rand do it may be more devastating than, say, having Moridin go around balefiring everything. Or that it wouldn't have all the desired effects.
