The Ogre Battledriver seems a little redundant. Since all your creatures (other than Renegade Krasis ) can come in with tokens, I'd rather just go with a 4th Exava, Rakdos Blood Witch and get in some more removal. I would honestly value more removal over Rakdos Cackler and Renegade Krasis since you already have such a strong mid-game win condition, and could easily get blown out by aggro. This might just be playstyle preferences though.

No I totally agree. I really don't like the Battledriver :P

However, I'm only running 3 Exavas because she's legendary, so I never want to see multiple. But with the new legend rule and the fact that she has haste, 4 is definitely a good option.

As for the Cacklers, I really like them (especially popping the opponent for 6 on turn 2 with Ghor-Clan Rampager )

The Krasises are not holding their weight in playtesting. I don't want to remove them completely, as I'd have nearly no 3-drop creatures, but they are a little too combo-esque (something I'm trying to avoid. Synergy = good / Combo = Fragile). Also, they were in there because they were easier to cast when I was only using shocks. Playing with all duals makes the Hellhole Flailer an easier cast.

So I guess that opens up 5 spots. I'm thinking +1 Exava, +2 Putrefy , +2 Shock . Unless, perhaps, you had a better idea?