[Sbetsho]

"That point aside, a real rinnegan master would never use the 6 paths of pain jutsu, because it severely weakens your powers, the only reason nagato used it was because his actual body had become crippled and was useless in combat. "

Quite the contrary. Using the 6 powers this way is way more effective than if you'd use it only by one body. Sensible use of synergy makes its parts greater than the sum of their abilities and powers.