I would go with Intangible Virtue long before I would go with Collective Blessing - sure it can win games, but the Virtue provides the tokens (the real focus here) with the bonus AND vigilance, letting them be defenders in the process.
The biggest problem I'm seeing here is that you're open to so much at the start as you're not going to want to block that Loxodon Smiter or other creature with your rampers. For this purpose, you couldn't ask for a better creature than Doomed Traveler. Easy blocker who gives you a 1/1 spirit that you then pump with the virtues - yes please. To that end, Midnight Haunting should probably be a 4x of - do not estimate how powerful flyers are in standard right now. Most people are running some zombie build or something to that effect and you can easily fly right over the top and beat their brains in (why do you think Delver was so nasty and Restoration Angel is still such a big thing).
I would also suggest lowering the counts of Parallel Lives/Collective Blessing to either 2x of each or 3-1 in whichever direction you prefer. If you consider that as a turn 3 or 4 drop (even with the ramping), you're still looking at trading an enchantment that doesn't give you any immediate benefit for their ability to play something much bigger (i.e. Deadbridge Goliath, Splatter Thug, Geralf's Messenger, etc). They're nice, but in reality you want to swarm them as quickly as possible.
I would also say to lower Sundering Growth to 2x in the mainboard and save the other two in the sideboard - sure you can use it for a quick populate fix, but if you don't have artifacts or enchantments to target, you could easily have something better there.
Also, looking at the sideboard (not sure if you're trying to keep this standard legal or not), but Surgical Extraction rotated out. So that'd be a no-go.
You also want to get this down to 60 cards if at all possible.
So, in sum, I would do the following:
-3 Wayfaring Temple (or at least -1)
-3 Sundering Growth (and then +4 in the sideboard)
-2 Akroma's Memorial (with any luck, by the time you have 7 mana you're doing a LOT more, making creatures and are overwhelming them)
-1 Growing Ranks
-1 Parallel Lives
-2 Grove of the Guardian (the 8/8 is nice, but he's slow and hard to get out - the colorless mana doesn't really help you either as almost everything is a white or green symbol)
-2 Forest
-1 Plains (You really will need Temple Gardens to be competitive)
+1 Midnight Haunting
+3 Intangible Virtue
+1-4 (however many you can get) Temple Garden
+3 or 4 Doomed Traveler
These changes SHOULD lower you down closer to 60 and would really hone in more on the idea that you're going to overrun them. I would then make up the sideboard out of removal and stuff (i.e. Pacifism) as your goal isn't to make a bigger creature than them, it's to make a LOT more than them and slide in for the victory (which sort of makes those spirit tokens that much more important). But I've found that without some sort of card draw, anything over 65 cards just won't give you the consistency you want.
And it's alright to be struggling with the idea, as I have a populate build that I'm still working the kinks out of. You can see it here:
http://deckbox.org/sets/239316