Problem is all we have for the pair of them is raw skill for the most part. Saesee has some nice physical and force feats here and there but I see nothing to suggest they can deal with Grievous' overwhelming physicals and unpredictability. Going by feats, one good kick would take Drallig out of the fight permanently, unless he has durability feats I'm unaware of.
Still not seeing what's so special about this duo. Are they very skilled? Yes. But Grievous is evidently more skilled than both of them and a lot more powerful physically. If Anakin can bat Drallig away with one arm Grievous can definitely find similar success. They would be unprepared for his unorthodox fighting style to boot, and speaking of boots neither have any durability feats to suggest a good kick from Grievous wouldn't crumple them.