Don't use Entreat in this deck, most of your ramp is gonna come from the sage as you'll likely only get 1 and maybe 2 pilgrims out in a game so it would be wasted, Sigarda is a good option tho.
Pacifism... That's a tough one, I've never once drawn an O-Ring and said to myself "I wish this was a pacifism" but I have said the opposite, I can understand it if you decide to go for Planar Cleansing as your board wiper but other than that I don't see it working too well. Moral of the story I like Oblivion Ring alot better but it's up to your playstyle, I hate to see planeswalkers on the other side of the field. I don't know what you mean about Mana Screwing tho, not unless they're using Mana Dorks since O ring can only hit non-land permanents.
What are you missing in green you ask, why the best card in M13, Rancor!! Yes I will continue to blab about rancor until you're sick of it, but it wins games there's not much to argue about that.
Honestly Nevermore is an ok sideboard card but usually decks don't rely on one certian card and if you're able to get up to 3 mana and your opponent 1 doesn't have a delver out and isn''t able to leak your nevermore they have no idea how to play delver, lol
Speaking from experience, ground seal is junk, I hate to say it because it seems good but literally the only thing that it can stop is Snapcasters and in that case you're still better off with Grafdigger's Cage, I found that out the hard way
Scroll of Avacyn is interesting, I've usually found that it's not worthwhile, by the time you actually get an angel out you'd better hope that you don't need that extra 5 life and card cause it usually won't be enough.
Defy death seems to me more like a sideboard card as Anti-Mill, casting a 10/10 Avacyn for 5, sounds good to me, lol
This deck looks pretty similar to my original Humans and angels deck, I've found that Naya actually works out alot better, especially looking at non-rotating cards, if you're willing to lose a little trade value/cash, Huntmasters are amazing, it's like card advantage stapled to card advantage every time it flips. I also love Gisela, and I would recommend just putting one in, it's usually worthwhile as a 1 of since it ends games way faster than Avacyn does. If you decide to add Gisela I'd at least consider Birds of Paradise, they're really important if you decide to go for 3 colors but that's just me plugging what's worked out for me, I think GW can be awesome on its own, The overseers are really awesome
Finally a couple of the white soulbond humans are awesome in GW humans and angels, namely Silverblade Paladin and Nearheath Pilgrim
Well that's my rambling 2 cents, hopefully something in there helps/makes sense, good luck!