I observe the opposite when I play football with my mates. If an individual or even whole team gets angry the performance usually drops. Some start blaming each other while others lose focus and make even more mistakes.
I don't think you are talking about classic anger. It is more like an combination of persistent character, determination at what you do and self challenge. I too feel the urge to do better and to outperform when something goes wrong but I don't think that is anger.
Well the reality of the situation is that different humans react in different ways to different emotions in different situations, so yes most people may get sloppy when angered while some can channel their anger for as long as they have an objective in front of them.
What I think the Sith teachings do is let anyone who gets properly trained gain that ability to focus their emotions into power without being enslaved by them and get sloppy, like Palpatine said "I can feel your anger, it gives you focus, it makes you stronger"