But that's not exactly true for incarnation unless they change the energy givin for starfire and Wrath. I'll use starfire as an example since it's an easier number scale to handle.
Current: Lunar - 0: 5 starfires (5 gcd's) 0 - solar: 5 starfires (5 gcd's) 10 starfires total to go from Lunar - Solar
Incarnation: Lunar - 0: 10 starfires (10 gcd's) 0 - Solar 2.5 starfires (3gcd's) 13 Starfires total to go from Lunar - Solar
Now obviously this is open to change a tad because of starsurges but on average, wit incarnation you're doubling the longevity of Lunar, however you're trip from 0 - solar isn't EXACTLY halfed because you can't cast half a starfire. Even with a starsurge it would not help. Not sure how the math for wraths work out, but everytime you go from Lunar - Solar you're going to be wasting energy. So you're not getting 100% benefit from the talent, where as Soul of the Forest will always give you 100% benefit. And as i stated earlier, a boomkin will benefit more from faster transitions rather than prolinging a single eclipse.
As for the treants vs. mirror images the game will explode from having 6 pets out at once! But no, treants as they are now aren't a super huge cool down as is (think they do like 150K damage assuming they stay alive the entire time?). So why not replace the lil stumps with three awesome temporary feathery friends of your own? Fairly certain mirror images do more damage than treants. Could be wrong though