well from the looks of it your trying to keep the deck in standard format 
1) add a couple more Parallel Lives. remember they stack well 1 token = 2 =4=8=16 a quick way to build an army with little effort
2) if you were willing to splash black you could throw in a couple Corpsejack Menace and a couple Common Bonds this combo would make your monsters pretty epic fairly easily. With a Golgari Guildgate and Golgari Keyrune you can splash quite easily. Also Death's Presence would help this combo also. Add in Gobbling Ooze and you can have a lot of fun with it.
3) you want to add a Growing Ranks. Phantom General is nice too. Power up them tokens lol. Slime Molding would fit in here also.
here are a few suggestions use em don't depending on your play style and what not also Wild Beastmaster i would get rid of yeah when it atks it buffs your other creatures but if it isn't buffed itself it doesn't help much at all best case scenario i would use it as filler or in a different deck. that's just my opinion though.
 

Yes Intangible Virtue would work better probably because less ways to destroy it lol i like the trostani it will fit nicely on the garruk u could use primal hunter or wildspeaker the reason i meantion wildspeaker is because he summons tokens and has a overrun ability which will help u finish the game

What to cut :
Sphere of Safety
Mana Bloom
Tablet of the Guilds
Courser's Accord

Switch Rootborn Defenses (more) & Druid's Deliverance (less).
Look for 'creatures with benefits' such as Geist-Honored Monk , Attended Knight , Captain of the Watch , and of course the new worm. Intangible Virtue is a definite 4-of.

Splash black and you have Lingering Souls and Vault of the Archangel , which would be brutal in this deck with Collective Blessing .

i agree with the tablet, sphere, and Courser's removal but if your gonna splash black mana bloom will be a nice way to get the black mana you need with out wasting a mana source. Also i like the ideas for Geist, Attended and Captain if your looking for a Planeswalker to add in here i would seriously look @ Ajani in combo with the splash black i suggested u get +1/+1 counters and when big enough u get quite a few tokens (lets say your life is 15 atm use ajani's last ability that 15 tokens plus if u have 1 Parallel Lives = 30 tokens if u have 2 thats 60 if u have 3 thats 120 and if u have 4 thats 240 tokens uber army in seconds) also look into Primordial Hydra w/ Corpsejack Menace combo and u have a very powerful angry hydra rofl

I'm not sure any card costing ccc really belongs, though. You have 12 duals, but two of your lands exist to be popped.