Too many people think bad DPS simply don't understand - that's really not the case - some people like me understand perfectly fine, but can't think and execute as quickly as needed.
This too. Playstyle makes a big difference. Some players naturally have a 'killer instinct' (or less dramatic characterization) for playing DPS in MMOs. Some players are naturally good healers and have an intuitive sense for damage intake and pre-emptively countering with heals. If you can solo heal Titan HM (back in the pre-i90 days) while stoned, drunk, half passed-out, with one hand on the keyboard, you probably have a very good natural aptitude for healing mechanics in MMORPGs.

Trying to analyze this is possible, but mostly boils down to "instinct". You're either a natural at the instinctive stuff, or you can learn it through a lot of practice. Sasukes and Narutos do, in fact, exist.