Riven buffs on PBE are not the correct direction at all
The Ultimate buffs do nothing for her as she is more than likely already overkilling her targets at the 33% thresh hold, increasing the minimum damage does nothing but reduce Rivens skill cap and give her power where she does not need it. Riven does not use ultimate early to put damage out, she uses it to kill 80% of the time with 20% of the time to push AoE damage in a teamfight or a very niche fight.
The normal build ( although Adrian Riven has recently started putting more points in W before E ) was to max Q then E then W, so the W bonus AD buffs basically do nothing until mid/late game with the exception of helping to clear out back line minions at a certain point.
The only thing Riven needs is 2 seconds back on her E, and 1 second off her Q to make it 11 seconds flat at all ranks. This would give power back into good Rivens who know how to chain Q, know when to shield and how to position correctly in fights. Reducing her CDs indirectly increases her damage without actually buffing her base damage.
SHE. DOES. NOT. NEED. DAMAGE.