You're saying the Pattern is able to create Ta'veren in such a complex way as to balance one another out to just the right degree to get the Bore sealed with saidin so that the taint can be Healed by saidar 3000 year later.

If the Pattern can do THAT much fine tuning, then why not just create a Ta'veren like Lews Therin of sufficient strength to pull the right bunch of scientists together to create the Choedan Kal in year 1 of the War, incinerate all the forces of the Shadow in a single worldwide attack, and then spend the next 10 years with no pressure with thousands of the most eminent scientists in the world studying how best to close the Bore.

And each time a new bunch of Friends of the Dark arise, they just get wiped out again by Lews Therin wielding the Choedan Kal.

Why this convoluted need to create ta'veren, and counter ta'veren, which leads to the desperate situation where the Dragon is facing imminent defeat at the hands of the Shadow, which drives him to attempt the Sealing of the Bore out of pure desperation?

No, if the Pattern is THAT powerful, it could far more easily have brought together the required scientists to build the Choedan Kal up front, and remove the desperate need for the Strike at Shayol Ghul in one go.

Sometimes, I think, we tend to overestimate the level of complexity that RJ planned into this story. Mostly, he just needed something for dramatic effect, or to keep the plot moving.