In a cube small enough to only use three nonland cards, I don't think the Wrath is necessary. It's a good card, but it adds to the critical mass of great wraths for bigger cubes. If it's causing you to exclude Hallowed Fountain(!), it's not worth it.
Black Sun's Zenith. I found Barter in Blood was awesome some of the time, but a lot of the time it would get stranded in my hand because sacrificing two creatures would still leave my opponent in a game-winning position. I'd rather have a more dependable Wrath.
Since the -1/-1 counters stay, you can't really compare it to the damage based Starstorm (which I still run, btw). So, even if you don't have the mana to kill all creatures right now, at least the surviving ones will become pretty small in the process.
I decided to up my cube size to 600 from 540, among those 60 cards I will (re)introduce some hard to cast cards like Geralfs Messenger or Seismic Assault, to make these cards playable I am upping the size of each guild section to 12 (from 10), with the condition that I add 2 dual lands to the mix (to make casting easier). But, you may have guessed it already, Golgari is harsh. From these 13 cards, what should I cut (keeping in mind that I would like to cut a non-land, but cutting a land is a little bit fine too).
If we exclude the Signet from Ausschliessi's list for a minute, that leaves only seven true multicolor card slots. That's the same amount per guild that I run at 720, and it's just right for me. So while I think it's on the high side at 600, it should still be fine in the short term, at least so you can identify the weakest link and plan future cuts accordingly.
I think Vraska is the best one of those four. And with her already chosen, the need for the other two removal spells goes down. So, Vraska and Shaman sounds good, even though I am not entirely sold on the latter.
Personally, I like Putrefy a bit more than Abrupt Decay. I think Putrefy is better in larger cubes, where the 3- cost enchantments and planeswalkers don't show up that often and where the general mana curve tends to be a little bit higher.
I would just cut Baneslayer Angel, since she is much more likely to not give you your investment back than any of the other cards.
:o!!!!! That can't right. I don't care how much you value EtB effects. Baneslayer can just run away with games. Far more games than silverblade paladin. I think if I was going to cut a creature from that list it would be silverblade paladin or mirror entity. Those two cards are less likely than baneslayer to give you your investment back, they are both 3cc which is what you stated you wanted to cut, and neither has EtB card value. Silverblade is only good with another creature, mirror entity is only good with a lot of creatures, both die to every removal spell in the cube including burn, and both are board situational unlike baneslayer which is a house in most situations.
Cut baneslayer, what kind of world are we living in?
That's not a fair evaluation of BSA. BSA is the epitome a good creature that can fail the doom blade test and still be good. She just swings the game entirely in your favor if she survives, and stops your opponent from attacking the turn she hits the board. This is all good because she is severely undercosted.
I would cut Hero of Bladehold over Baneslayer anyday, and I wouldn't even recommend cutting hero before all the other cards.