For those whou wouldn't have followed our previous episodes, Tortured existence.dec is based on the eponym enchantment, and intends to find creatures solutions through it, using a lot of dredge and graveyard manipulation.

Last build was a classic GB deck, two well known colors for any who plays reanimator things.

Tactics

When I tested it, I observed a few things.
First, something you might already know the deck is slow. Llanowar Elves or Elves of the Deep Shadow can't help this.
Second, as it's slow, you can't afford to misplay. A lot of testing is not necesseray, it's essential. Basically, your first hand needs at least one creature with sacrifice ability (Spore frog or better, Sakura Tribe elder), at least one dredge able one (Golgari brownscale if you play against anything damaging quickly your life total, or Stinkweed imp for a quick graveyard fill), and of course at least one Tortured existence. With 2 lands, you're on the go.
Third, as there are a LOT of interactions, you do need to test (yeah, I know, I tend to repeat myself). It's useless to play four Golgari Brownscale if you forget to spend all your black mana into torturing them in and out of your graveyard by the end of your opponent's turn. In the same way, you may want, as your turn begin, to proceed like this :

You're at your turn 3, you already have 3 lands and a sakura tribe elder in your graveyard (wonder how these 3 lands reached the board...)

Untap step : untap 3 lands
Upkeek : Torture one brownscale to get one sakura tribe elder back
Draw phase : dredge your brownscale, get 2 life and possibly two tools you can torture later
Main phase : Play your sakura tribe elder.

So yes indeed, you don't have mana anymore, since you spend all 3, but you draw what you wanted to (a sakura tribe elder), gained 2 life, have a blocker/mana tutor on board and filled your graveyard with creatures. Not that bad ! If you consider that you may have a Spore frog layed on turn one, it can be very strong against aggro. For some example...

Third, and last, don't make it slower than it is. As soon as you can cast a Blastoderm, go for it. It doesn't mind if it gets countered, you will have your revenge next turn. The same can be said of Dimir House Guard : tutor your kill as soon as you can, it can't get countered ! And, again, you can get it back ! All this doesn't mean you have to rush in : it remains a control deck.

Changes

Ok then, these are tricks, but are the changes you talked about ?

Here's the new build the tests gave birth to.
Lands
8 Forest
12 Swamp

Creatures
1 Faceless Butcher
1 Nantuko Vigilante
2 Blastoderm
4 Eternal Witness
3 Spore Frog
3 Stinkweed Imp
4 Dimir House Guard
4 Golgari Brownscale
4 Mesmeric Fiend
4 Sakura-Tribe Elder

Other spells      
1 Æther Vial
4 Tortured Existence
4 Culling the Weak
2 Duress

Sideboard
1 Ravenous rats
3 Crypt Rats
3 Ghastly Demise
3 Nantuko Vigilante
2 Duress
2 Blastoderm
1 Spore Frog

Elves, or Yavimaya elders are out, and replaced by 4 Culling the weak. You wanted mana acceleration, here you are. Talking about mana, mana base last build was all screwed up, with basically 8 swamps when you need 12 of them...
Demonic tutor is a great card to go through your library. Eternal witness is just better when you need to get things from your graveyard. More over when you think it is a creature, and can be brought back to your hand thanks to Tortured existence. You therefore have the new name of the deck : Tortured witness.

Other options

Can it be bettered still ?
I don't know yet, but I'd like to playtest Tortured witness with some cards from Timespiral. 2 of them focused my attention in making the deck run way faster and more secure.
The first one, a security one, would be a replacement for Spore frog : Children of Korlis. It would indeed mean you need a source for white mana. Wild cantor seems the perfect candidate for this. It could fit in by getting out a couple of lands, as a recursive mana fixer/beater. To be tested though.
The other one, less important, would be Pit keeper, a Tortured existence on legs. It could help by saving mana, beating and be another target for Culling the weak. I don't know yet where to squizze it in, but will keep you posted with playtest results as soon as I get 4 of these.

The last option can be tested by now just as Wild Cantor. It would be a nice option to make the deck faster - and by this I mean "more aggressive" : instead of Blastoderm, play Nantuko husk.
Both Blasto' and Husk are vulnerable against MBC, that forces you to sacrifice, and doesn't target.
Just as the big green thing, Husk doesn't fear burn as long as you have creatures on board. Okay, if you don't have any, it's too bad. But Husk is out there one turn earlier. Which brings Husk's main default here : it can't be reached through Dimir House Guard.

The match is pretty even yet, and I will compare these guys very soon through playtests.

To conclude, I just had an awful idea by writing this article up, and will let you know very soon. Just a clue : Ugly Legends art (yes there are a few...).