Well first off, it's not an aggro build by any stretch of the imagination (as aggro decks are aimed to be MUCH faster than what you're looking at here - your first creature(s) can't even hit the board until turn three when you would cast
Midnight Haunting).
That aside, I would move a few items from the sideboard into the mainboard and vice-versa. For instance,
Rootborn Defenses is a great card, but it doesn't really fit what you're looking to do here unless you need to protect against board wipes. I would move it to your sideboard and but both the
Avacyn's Pilgrims and the other
Farseeks into the mainboard. I would also reduce
Collective Blessing to a one or two of, if not completely drop it. If you were sitting on an army of tokens, then I could see where it would give you the killing blow. But given the current build, you're going to be pumping what, 3-4 creatures?
Since you're aiming for mid-range, I would suggest potentially tossing in
Ranger's Path or even
Seek the Horizon to try and help you get to the mana you need to cast
Angel of Serenity/
Thragtusk faster. Sure
Thragtusk can help you regain the life you lost in the first few turns, but it's easy enough to deal with. Perhaps
Centaur Healer could help fill the void and cover your rear until you get to the mid-game, where you would be free to dominate. (Specifically, I'm thinking about how
Geist of Saint Traft has you hurting pretty long before you're going to hit a tusk.)
As much as I hate telling someone to add $80 worth of cards to a deck, you really need at least one or two
Cavern of Souls to stop a pesky
Syncopate or
Essence Scatter from messing you up.
Lastly, given the usage of white, I would advise 3x
Nevermore in the sideboard. It's easy enough to move in after you get a sense of what your opponent is doing after the first game and it can completely hamstring an opposing deck. Just think about how much it would suck if someone cast it against you and named
Thragtusk or
Angel of Serenity...