Most of Juggs' damage comes from abilities with 90% accuracy (rage builder)
First off, the only attack that Jugg/Guards use that has the 90% baseline chance to hit is Strike. Sundering Strike isn't considered a basic attack and, as such, benefits from the 100% base accuracy of Special M/R attacks.
Secondly, you get the Focus whether you hit with the Focus generator or not. Missing only affects your damage, not your resource generation.