Primary statistics affect the cooldown of your various skills. There are three stats and they each affect a single ability. Really, each stat is just an “ability buff” for one specific skill.
- Strength: Affects the cooldown of your melee ability. The default cooldown is 60 seconds and at the Strength cap you will have a cooldown of about 20 seconds.
- Discipline: This affects your grenade cooldown, again, 60 seconds to 20 seconds.
- Intellect: This affects your super, it takes it from 5:30 to about 4:00. It also increases the amount of super you earn per kill.
The suggested cap for each skill is 170 points at level 20. The cap at level 30 is suggested to be 270 points.
- Intellect (Super): 5:30
- Discipline (Grenade): 1:00
- Strength (Melee): 1:09
- Intellect (Super): 3:55, Twice as much Super Meter earned from kills
- Discipline (Grenade): 0:27
- Strength (Melee): 0:31
So on average, it takes
1.05 points to reduce the cooldown of Super charge by 1 second
3.03 points to reduce the cooldown of Grenade by 1 second
2.6 points to reduce the cooldown of Melee Attack by 1 second
Reference: Destiny in Numbers: Cool Down Reduction