The buffers in the sa'angreal are mostly buffers against drawing too much power. However, angreal made after the Breaking might have contained buffers against the taint. Maybe. Callandor was made DURING the breaking under special circumstances by the Aes Sedai who foretold the Dragon's rebirth. It would be safe to assume that THESE Aes Sedai, unlike the "modern day" useless ones, actually knew what they were doing and designed it to a specific purpose that only they know and we must wait and see.

Plus, the Aes Sedai of the AoL didn't know about the true power until Mierin (Lanfear) detected it, realized men and women could both use it, and tried to tap into it effectively boring into the Dark One's prison. Any angreal made before that could NOT have a buffer against the true power in it unless it was a complete fluke. But, any angreal made after the bore was made probably has either a buffer against it OR a means of using it more easily (Callandor?)

Interesting theories.