Let me first say I love Grixis control; I've been running it since Innistrad. My current build has now taken first at two FNM's, so any suggestions and critiques I offer are understandably based on that build. Hope I can help you.
First, the mana base as you said you have some color issues. I run playsets of the relevant duals,
Bloodcrypt 
,
Steam Vents 
,
Dragonskull Summit 
,
Drowned Catacomb 
, and
Sulfur Falls 
. The wonderful thing about it is that with just one shock in play, the other three duals all come in untapped. And with eight shocks, it's not hard to hit. The Cavern strikes me as a bit odd as well.
Desolate Lighthouse 
has served me well, letting me dig into the deck mid to late game.
For the aggro issue, I run planeswalker light. 2x Lili's and one Bolas, Bolas being sided against aggro.
Vampire Nighthawk 
is great as it gives a good blocker, can take on big threats, and most importantly gains you like that is sometimes sorely needed.
Magamquake 
also shines, being instant speed and leaving the board, with the exception of perhaps a snapcaster you've used, untouched. I think you could also safely cut tragic slip, and go for
Izzet Charm 
. Has the potential to counter, and two damage at instant speed can go a long way.
And as a special note on this,
Tribute to Hunger 
has been an all star in most all of my matchups.
For other more general comments, the Lotus doesn't seem to be needed in the deck. With duals you don't need the color support, and with the draw power this deck can generate plus the support of snapcaster, you can go into the late game without the lotus. Jace also seems underwhelming, at least as a one of, and the Sphinx and harvester, while good on their own, I don't see fitting well into the deck.
