Another alternative is grouping with a rogue who will benefit from the revitalize proc and actually deal some damage. If a single rogue constantly has 4 wild growths and 4 rejuvs on him, then I believe the math would be as follows:

Wild Growth: 7 ticks over 7 seconds
Rejuvination: 5 ticks over 15 seconds

Each has a 15% chance to restore 8 energy.

Over a 105 second duration, on average the rogue will have 140 ticks between both spells per druid (15 casts of WG for 105 ticks and 7 casts of Rejuv for 35 ticks) which means for 4 druids it's 560 chances. At 15% per proc, that means it will proc on average 84 times, which will restore 672 energy. Normalizing down to 30 seconds, that means every 30 seconds the rogue will on average get an extra 192 energy... that's quite a bit.

Did I just rape the math? Haven't double checked it yet...