pinnacle is 1560.
atthe end of season by farming activities you can get +20 at most. resulting in 1580.
having an activity at +30 (1590) is an iextra grind no one wants to do.
nerf their activity level down to +20 (1580).
1590 activities in today's destiny is not granting any loot worth chasing.
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They are meant to be done under leveled. They want you going in at a disadvantage to make it harder. The vast majority of this game is painfully easy. No reason for them to nerf the few hard activities they have.