Standard: Gain Life and Grow

Voracious Wurm + Heroes' Reunion is a 9/9 on turn 4. Last time I checked, that's pretty difficult to beat.

If I were to build a GW Life based deck, I would want to focus around Angelic Accord. That means that I'm focusing on gaining at least 4 life every turn. Once you have that, the game just falls into place. If your intent is to just gain life, you may feel content if you're gaining an average of 1-2 life per turn. Unfortunately, most quality aggro decks can do more than 3 damage every turn without breaking much of a sweat.

So while you already have a decent idea of what you want to be doing, I would suggest ramping it up a bit. Some things that you definitely can benefit from would be the Angelic Accord, which provides you with bodies that you may otherwise be lacking when you choose to turn on the life gain package. Riot control could really benefit you, as it will essentially buy you an extra turn, on top of pushing you even more forward in the life race. For another real bomb, you can put in Nylea's Disciple. You will spend your first few turns filling your board with green things (Experiment one T1, Caryatid T2, Bow of Nylea T3), then drop the disciple to gain 6 on turn 4, and have plenty of decent sized bodies to work with.

I really like the bow of nylea in this build, because 3 life per turn can really snowball in a drawn out game. I think 2 is a solid number for this build.

If you ever want to do well with any deck in this meta game, you're going to need lots of, or no removal. The removal that you have right now - Pacifism and Arrest -, while they can be effective, won't really get the job done against the aggro match up. I've learned by trying to play the same number of Chained to the Rocks + Detention Sphere in my UWR list that just having 7 removal enchantments won't cut it today. Not to mention that Chained and DSphere are more effective than Arrest or Pacifism. Right now, GW doesn't have too much else in the way of removal, so I would forgo it entirely. You aren't building up to white devotion, and by playing the enchantments over something that will advance your state is just going to slow down your whole game. If you feel that you really need removal though, I'd play a playset of Selesnya Charm. It will deal with anything that your centaurs and such can't (Desecration Demon?)

I can understand how Predator's Rapport and Staff of the Wild Magus may seem glamorous in a life gain build, but they're really not all too fantastic. The staff won't be doing anything near as much as other cards in these colors will, and by the time you'd want to play the Rapport, you should already be winning anyway, and you shouldn't need the extra life (Sure, gaining 40 life off of a 20/20 wurm seems awesome, but you have a 20/20 wurm... You don't need 40 life on top of that).

Your current creature suite seems pretty solid right now, actually. If anything, I'd put in the Soldier of the Pantheons just to have more options for turn 1. They evolve your experiments, and can help out in the control matches with the pro-multicolor.

That's about all I could think of at the moment to help out with this. Hope your changes are successful!

I was thinking that he was budget oriented... Totally forgot that archangel is a $20 card.

But yes, if you can, add all the trostanis. As Ty said, with angelic accord, you'll pay 3 for 8 flying power and 4 life (1 angel from Trostani's populate, 1 from the 4 life you'll get EoT). With Bow of Nylea as your early game engine, and this as your late game engine, you should have no problem outlasting any aggro deck.

I also second Advent of the Wurm. At best, it's a 5/5 for 4 that will net you 5 life and an angel on your opponent's turn. At worst, you take out their counterspell for 4 mana and are free to bash them with your already huge field.

And on that note, if control is a problem for you, Loxodon Smiter is a fabulous 3 drop that you can add. Cant be countered, will net you another angel with your trostani accord combo, and offers a huge body very early.

wow, thank you all so much for the great advice.  I am making some changes to the deck based on this.  You all are awesome, and I appreciate the help.