Though, from what I understood of ta'veren, the Pattern, and such that the Pattern allows for free will. It was discussed in the Eye of the World. Little changes, are alright, it is a pattern after all. Big world sweeping changes, are what ta'veren are for. To change the Pattern, or be pulled along by it to those changes, and to draw others around them along those changes.
As long as those goals are met the Pattern doesn't care. The Dark One is outside it's calculations. With the Dark One the Pattern can only be reactionary. As long as keys points are gotten too, the how of it matters little.
I think if Rand hadn't channeled the True Power, the Dark One would have won. He was in a situation he could not excape otherwise without outside intervention.
There is a saying. One death is a tragedy, a thousand a statistic. The damage and suffering Graendal could have continued to cause if left free would make a few hundred deaths acceptable. Rand had a lot of tools in his arsenal, but Balefire with its risks was the one he depended on, not just to kill her, but to ensure she stayed dead!
As to Egwene...she viewed she was sparring the Aes Sedai.

For us impartial observers it is easy to accept, or condemn, but the charachters motivations and goals need to come to mind too in any debate.