I made a video about my thoughts:
Soul of the Archdruid: Gain the Soul of the Forest talent.
I think with this legendary we could almost have a 100% uptime of SotF buff. This is with the help of prosperity and tier 20 2-set bonus. Either way this legendary makes the tier 20 2-set bonus MUCH more appealing.
With swiftment buffing SotF and efflorescence (tier 20 4set) this will increase Resto Druid burst healing massively!! Considering the best 2 legendaries for 7.2.5 would probably have been Trinket and Neck, this is a way more fun than taking less damage