I doubt any of the rulers at the Field of Merrilor on the eve of Tarmon Gaidon will care all that much about the fact that the Oath Rod cuts down a channelers' life span (some might even think that's a good thing).

I'm of the opinion that Cadsuane is among the Sisters who would think the Oath Rod is still important, even if it negatively affected her lifespan - she doesn't seem like the type of woman to be horrified at the thought that she might die after having lived a long and very successful life.