Consider adding Contagion Clasp or Contagion Engine . They both have a bit of spot removal that plays around indestructible creatures, and the proliferate function helps the Luminarch Ascension and Elspeth, Knight-Errant . Alternatively, since the land requirements are so lax, you could put in a few Island s or Glacial Fortress for card:Tezzeret's Gambit (one of my personal favourate cards), which is very relevant for the card draw and the proliferate. I know it has Phyrexian Mana, but you probably want to avoid losing life with the ascension going on. If nothing else, keep these in mind in case you have trouble getting any cards because these ones are going to be pretty easy to obtain.
I'd consider Student of Warfare , he's a pretty amazing 1-drop.
I also agree with ldumonceaux, testing with proliferate might prove to speed your deck a bit.
splashing blue would also give you access to Wall of Denial , which I think you might love.
Thanks for the suggestions, you guys. I'm going to make another version of this deck with blue splashed in it and test that out. I'll update this one with some of the white changes too.
Also, I can use the phyrexian mana to play card:Tezzeret's Gambit since Luminarch Ascension checks my life during my opponents' end steps, not mine.