You may already know this, but there's no reason to have the gates that produce black mana. Compared to the other gates you have, they're less flexible. You can have multiple copies of the same gate in play, so I'd suggest running 2 G/W instead, or maybe 1 G/R and 1 W/U, or some other combination of the colors you're already using.
If
Hold the Gates and
Risen Sanctuary are central to your strategy (and
Hold the Gates definitely seems to be), then you should have more than one copy of each. Right now there's only a 25% chance that you'll get one of those by turn 8. Eight turns is a long time to wait, and you'll only have the card 1 in 4 games. And what's worse, you only have a 6% chance of drawing both of them by turn 10. If the rest of your deck was highly tuned for stalling, you could do it, but the better option is to improve your
odds.
I would also consider whether you really need
Battleflight Eagle,
Righteous Authority, and
Firemane Avenger. It seems like they add the least amount of power to this deck, and they're inflexible.
Angel's Mercy does work at instant speed, but so does the triggered ability of
Font of Vigor, which may be better.
In the end, this is just advice from someone on the Internet. You're the one who plays and tests the deck, and you'll find more ways to improve it, I'm sure. It does look fun to play.