Rot Farm Skeleton doesn't seem good enough for constructed play, maybe replace with Farseek since your curve seems pretty high (with Ghoultree, using Varolz's ability and few very cheap cards - not to mention the possible inclusion of Deadbridge Chant).
I'd also consider the antisynergy between Ghoultree and Ghoulcaller's Chant, but maybe the latter is good enough to keep in anyway.
Veilborn Ghoul could be a surprisingly awesome card for this deck. I'd pull out the skeletons and try them instead. Also, Mulch is a thing and would work better than you probably think it would in your list. People who think Ghoultree is a high curve card aren't getting it, which is why you should explain what your going for here.
Basically what you have here is an updated version of "Dredge 2.0" which was a rogue deck before Gatecrash(I remember seeing it do the occasional thing at a tournament here or there, but since gatecrash I haven't seen it anywhere. I think people are really afraid of Rest in Peace which confessedly just ends the match if it resolves.)
Jarad is also a good idea, along with Splinterfright which isn't just big in a deck like this, but also tramples and keeps dredging you every turn.
Also with decent sac outlets, and decent removal in the deck, it's probably worth considering Tragic Slip as a follow up removal for cheap. If not main deck, it could be a solid side in against decks faster than yours. It kills most of the early hasters for red black, including the new 3/1 guy for 2. It kills anything after something dies, and your deck can do that easily with gravecrawler + sac outlet, or just by suicide attacking in with gravecrawlers.
I think this deck is a good idea, and was exactly where I personally wanted to go with Varolz. Only difference is my build is much more aggro and will utilize Blood Scrivener
The point here is pretty simple, run headlong at the enemy while putting out a force that doesn't die/gets stronger. Gravecrawlers allow for big Bloodthrone hits, Blood Artist recovery, and big Lotleth Trolls. Veilborn Ghoul allows for pitches to lotleth while also being something for the late game to throw down if you get swept and need a quick zombie to get things back with. I've made sure to include plenty of ways to get to swamps for this reason, and evolving wilds with the dual lands allows for 12 ways I can get to a forest when I need one.
Evolving Wilds is an easy way to power up filth, which in turn with putrefy allows tragic slip to hit something big.
Costs are kept low to activate blood scrivener, at which point drawing 2 cards and getting back resources should put your opponent, who, if he has survived, is probably tapped out of resources, into a vicegrip that leads to victory.
I took this version of the deck to FNM this past Friday, and placed 7th overall. I was rather pleased with it, but there where several things that irked me. I've got a detailed review for you of the matches and a skim of how they played out. My sideboard was very wierd so I am not gonna post it, I didn't have the cards I needed so I just gummed up a few things that I thought would work in a pinch.
Round one, I can't really remember what he was playing, I just remember I won 2-0.
Round 2 vs U/R Control 2-0
Game 1: On the play, I kept a pretty quick hand of Swamp, WC, WC, Grave, Mulch, and Dreg. After he knocked off a few creatures, I was able to stick a Jarad, swing in on the next turn, and finish off his last 2 with a reanimated GC sac.
Game 2: A bit more difficult this go round, but I started off similiar, only with a slightly slower hand, after having my first GC pillared I decided to play a Lotleth and just pitch 'em. He got in a few damage. I started baiting out counters/kills to fill my yard, and eventually windmilled a Ghoultree. Next turn I rancor'd it up, and took a swing, he went down to 8. He thought twice about it on my end step, drew and scooped.
Round 3 vs Wreckdos (B/R Control)
This was by far the most excrutiating match of the night. I had never faced this deck before and found it to be an uphill battle the whole way. This was the only match for me that has ever gone to time.
Game 1: On the play, I zerged the field out of the gate, I drew into 3 Dregs before he managed to kill one, with a rancor'd up GC it was an easy win. I didn't sideboard as I didn't really have any kind of information on his deck.
Game 2: This is where I got to see what his deck could do, every threat I played was dismantled with kill spells, I eventually died to a Chandra and a Bloodhall working me down. I made him play out the whole thing and forced him to show me everything he had by continiously playing threats.
Game 3: I discerned that his entire deck was kill spells, a couple of Chandra's and a Bloodhall. I worked him down to 7 before he finally stablized, wiping the board, and playing a Curse of Death's Hold on me. I had to wait 5-6 turns, and finally got a Dreg Mangler to go hard in the paint on him to drop him down to 5. On turn 3 of time, he played a Vraska and attempted to kill my Mangler. I had sided in Ranger's Guile and windmilled it down, he was left with one mana open. On my turn I scavanged my mangler in the yard, and swung for game.
Round 4 vs Naya Blitz 0-2
This game was pretty awful on my part, as I really got hosed both times. A Mull to 5, and then getting stuck on 3 lands was pretty bad. This game doesn't even warrant a evaluation.
Round 5 vs Junk Reanimator 1-2
I had the option to 1-1-1 this, but I wasn't sure if I would be knocked out, having been 0-2'd in the previous round. So I went ahead and played it out. I still managed to top 8, but I wanted to test the waters against one of the more popular decks in the format.
Game 1: I was on the play and came out of the gate swinging hard, and eventually overwhelmed him before he could started graveyard shenanigans. He eventually died to a super rancored Dreg Mangler. No sideboard here.
Game 2: On the play, he started off early, I salvaged all I could but really couldn't hit enough tempo to get the job done. I got him down to 8, before I got a look at one of his sideboarded cards Crypt Excursion. He nailed me, then got a Angel of Serenity out of his yard, took all me threats and beat me to death. Sideboard -2 Varolz, +2 Silklash
Game 3: Pretty much went the same as the 2nd game, with me starting out strong, then pittering to a Angel. I had to Putrefy the Angel twice, but eventually I got overwhelmed when an Aurelia came in and took over the game, and me with no removal in hand.
vs. Naya Blitz 1-2
Rematch, only this time I put up a bit of a fight.
Game 1: He mulled to 5, and just couldn't get his tempo up, and when he did finally manage to get board presence, I just putrefied his threats, or blocked with Lotleth regens. I managed to go deep in the paint with a rancor'd Ghoultree. Side -2 Drown in Filth +2 Gaze of Granite
Game 2: Good start for Blitz, was impossible to keep up with him, swing for 19 on turn 4.
Game 3: Was an excellent game, we were throwing punches at each other left and right, but eventually he overwhelmed the board and with a battlefiend medic, gaze in granite was a late draw.
All in all there are a few things wrong with the deck. I'll throw a few of my major complaints out there, but other then these following few, the deck worked extremely well:
Drown in Filth
I often found myself having this in my hand when I would have really enjoyed just plain old fashioned spot removal. With alot of the meta in standard, I really don't think that it's right just yet. Sure it pitches into our graveyard, but alot of the time I found it pitching lands that I really needed or wanted, and it's counterproductive to our mulches. I'm taking it out and adding something new and docking this in a sideboard.
Varolz, the Scar Striped
I don't think this guy pulls his weight either. I'll be honest, I ran 2 maindeck, and saw him once the whole night, and I pitched him to Lotleth. I'm sure this guy has a home, but when we want to be pulling zombies back out, we really don't want him to be eating them.
So I think I'll be running this version next Friday.