SPQR_Destructus

You're going to want more creatures for sure, perhaps removing those Mastiffs as well.
Desecration Demon
Cartel Aristocrat
Sin Collector
High Priest of Penance
Those are nice cards for a BW deck.

Alright, I picked a few of the cards that RolledAOne did.

1. Simic Cluestone -- Works alright with your untap cards, but I don't think there's enough reason to keep it beyond that.
2. Simic Keyrune -- Same as the cluestone and the ability doesn't excite me.
3. Simic Signet -- Nice way to get the colors you need for land, but I don't think you'll have that problem with the types of lands you're playing.

4. Battering Krasis -- Sure it'll get pretty strong with evolve, but I think that you have better cards to spend 3 mana on.
5. Captain of the Mists -- I don't think you have enough humans + his ability will be rather redundant. Costs 3 mana and his ability is 2 to boot, I wouldn't keep him around.
6. Cloudfin Raptor -- Evolve on a flying 1 drop, but like Battering Krasis, that's all he is.
7. Fertilid -- Looks like a fun card and you won't have to worry about him dying at all from his ability, but he doesn't appear to be that strong.
8. Hero of the Leina Tower -- Pretty neat Heroic, but I don't think you'll need this at all.
9. Sakura-Tribe Elder -- You have to sac him and nothing in your deck works with that mechanic.
10. Simic Manipulator -- Works pretty well with your deck, cut just because you have to remove his counters. This is a big maybe.
11. Yavimaya Elder -- There's creature sac again. I don't know if you need this much ramp.
Now this is where you begin to question my choices.
12. Garruk Wildspeaker -- You might want to keep him in, but I'd replace him with Caller of Beasts.
13. Explosive Vegetation -- Ramp.
14. Life of the Loam -- How often are you going to have lands in the graveyard? I get a bit about how it works, I just wouldn't bother with it.
15. Rampant Growth -- Good ramp card, but I don't think you need it.
16. Seek the Horizon -- Second verse, same as the first.
17. Skyshroud Claim -- Same.
18. Urban Evolution -- I like it, but late game, I don't know if you'll need it.
19. Whelming Wave -- If you're going to take out ramp, I would take this out. On top of that, it'll wipe a lot of your counters and the ehll with that.

I realize that some of the reasoning/choices aren't that solid, but I hope that this comment at least helps on a few of them.