too many 5 drops, not enough early spells, overall way to slow. This article might be useful http://magic.tcgplayer.com/db/article.asp?ID=11215.

I would definitely drop Assemble the Legion and Hold the Gates for a number of defenders and kill spells. The legion isn't really relevant until T7-8 ish, and since you're not running removal you'll have lost by then already, against even midrange decks. Hold the Gates you -could- keep if you really, really like it. It does buff for a fair amount.

I don't think the gatekeepers are the obvious way to go. Sure you'll ALWAYS get your bonus of them, but really. The effects is easily achievable through better cards. Maybe Ubul Sar Gatekeepers , as he doubles as removal.

Angelic Edict is too slow. Run something like Searing Spear or Murder instead. Also maybe run Selesnya Charm , a that can help you make better trades in combat, flash down a blocker, or kill a huge threat.

I would also suggest, that you run Gatecreeper Vine as a 4 of. He's cheap, fixes, thins and helps you get to 10 gates faster.