I would cut underworld connections (not very good) and Mikaeus, the Unhallowed (you don't have any sac outlets, and only two creatures that sac themselves for any benefit next to Mikaeus). Arguel's Blood fast could replace connections.
I think with this many board wipes you should cut down on mana dorks a bit. Sylvan Awakening and Creakwood liege also do not seem very strong.
If you cut on creatures, cut Pathbreaker Ibex too.
I think your mana base is terrible.. to have Phyrexian Obliterator and Hornet Queen in the same deck is kinda crazy with budget mana. Woodland Cemetery, Llanowar Wastes and Overgrown Tomb are all affordable. I also think 36 is not enough lands with an 8-mana commander. I personally would play Ash Barrens and maybe some other land cycling.
Beast Within should be in the deck. Treasured Find is very weird. Regrowth is better. I actually think Greenwarden of Murasa would be the best pick here, and [card]Eternal Witness/card].
I am not a fan of Praetor's Counsel. I just don't see when it will be worth it in your deck.
But Erebos means you get a good (indestructible) body when your devotion is high enough, and it hoses lifegain incidentally.
Private Mod Note
Rollback Post to RevisionRollBack
Card advantage is not the same thing as card draw. Something for 2B cannot be strictly worse than something for BBB or 3BB. If you're taking out Swords to Plowshares for Plummet, you're a fool. Stop doing these things!
In terms of ramp, you'll need all of it. like, every possible iteration of any form of ramp. even the not-so-good-ones.
Your strategy is based around a 8cmc general, who you don't want to have die, so you gotta be able to cast AND protect at the same time. You'll need a LOT of mana for that.
I'd dropping a lot of your mana rocks and replace them with lands. 36 is very light for a mana-intensive deck (i think). I'd go upwards of like 40-45 actually. run things like nature's lore, sad robot, sprouting vines (cast it on an opponent's turn when they've cast say 2+ spells), reap and sow and tempt with discovery. yes, some of them don't seem very good, but you ABSOLUTELY need to be at 10 mana at least by the time your opponent is on 5-6. You want to be at your prime when your opponents are piling on pressure and all that.
Also, it could be a thing to more of those high CMC things in your deck and replace them with land-ramping. Especially those that don't help you win from behind (zendikar resurgent, mikaeus and grave betrayal). Maybe add some disruption like mass-discard that costs less than say 4cmc as well just to slow your opponents down so you can get time to catch up.
I've tried to make a sisters deck before, and it didn't end well. not sure what it was, but i gave up on it before i really tried to dive deep on it. I wish you the best though, and i really hope you'd find success where i failed.