For all my time spent with the Lord of blood, I still can't tell if he's the best caster in the game, or just the most fun. What could be better than a warlock that can chase an archangel for three turns before eventually killing it by himself in the opponent's deployment zone?
Extremely durable. Like, tank for your entire army durable.
Can easily kill two heavies by himself
Provides a universal defense and strength buff with proper positioning - and one that magic defenses don't help against.
Innate sacrificial pawn and steady
Extremely fun to play and paint
Relies heavily on star-crossed defense - which can sometimes feel like it does nothing.
Very slow (since the entire army stays behind him, and he only moves 8-10” a turn)
Very bricky - you tend to have 5-6 models attached to him, and the rest of the army wants to stay nearby
Low on points - between his low warbeast points and having to sacrifice 7-10 points for his feat
When I play Barnabas2, he is the very definition of a Frontline caster - usually he's the furthest forward model in order to apply Execration of Blackest Night as far forward as possible. If the opportunity to use Hunters' Mark or Rebuke arises he will sometimes cast those, but most turns he casts Execration of Blackest Night and Spiny Growth and charges forward into your opponent's army and hopes that they think he will die to just two heavies.
Barring stationary or Iron/Wild Aggression, almost nothing in the game can reasonably kill Barnabas2 camping 4 fury (unless he literally runs out of boxes in his battlegroup - which is possible, since points are super tight in his list and I tend to eat a warbeast in his battlegroup for the feat).
You just repeat that process until everything is dead, with the Valkyries taking stray shots and ranging forward with their threat 13 mat 8 pow 14s while everything else just follows Barnabas2 and kill whatever gets close to him.
Pieces that are absolutely required with Barnabas2:
Spirit Cauldron and Boil Master: they provide corpses for Barnabas2 before he feats, they provide a Puppet Master and they can Gallows if necessary for extra threat extension. They're not that expensive, and there's no reason you can't sacrifice the Boil Master to the Feat once the Cauldron gets in position
Gatorman Soul Slave: Onslaught is a surprisingly important part of Barnabas’ kit, so keeping it up for free is actually really important. He also brings a rat 4 boosted Hunters' Mark along with it, which is always nice. For reference, that's a little more accurate than Lanyssa or a Blackclad.
Bull Snapper: you need Spiny Growth, they're the cheapest boxes per point you can get in your battlegroup, (even when they're not free) and you can sacrifice them to the feat and reeve their fury (thanks to the Mordikaar Essence Blast loophole) to get a relatively cheap 3 fury.
Editors Note: The infernal ruling for this is found here.
Wrongeye and Snapjaw: it's another heavy, and one that's hard to kill with guns to boot, but more importantly, Star-Crossed takes Barnabas2 from hard to kill to nigh-unkillable.
Pieces I like with Barnabas2:
Dahlia and Skarath: They’re high defense, they’re steady, they help with high-defense living models (which the army otherwise struggles with), and Haunting Melody + Rebuke can shut down most of an army in the right matchups.
Boneswarm: You’re already taking a spirit cauldron, so now you get a pow 20-ish light that can go in first, make 4 attacks, then be sacrificed to the feat for 4 fury. Also, if you’re playing against Grymkin, you can stack Swarm, Spiny Growth and Execration of Blackest Night for maximum hilarity.
Farrow Valkyries: They reinforce everything the list wants to do - they’re high defense (for minions), they take really good advantage of Dark Shroud with their 2 high-pow melee attacks, they provide more shooting insurance (and you can move aoes that hit Barnabas directly extremely far with 3 sac pawns and 9 shield guards) - and they’re shockingly hard to kill (15/17 with 5 boxes is caster stats, and not particularly bad ones)
Farrow Bone grinders: Mostly there for Craft Talisman and being sacrificed to the Feat while still being able to do so - but again, if you find a living warbeast, they will mess it up thanks to Dismember or Grievous Wounds on their melee weapons.
Blackhide Wrastler: You’re taking at least 1 heavy, you should have access to Rage.
Swamp Horror: This one probably isn’t worth it because his defense is so low, but even a slow 15-point impending doom is worth considering for extending Barnabas2’s threat range even more. Really, it’s the MAT 6 that kills it for me.
Pieces I don’t like with Barnabas2:
Bone Shrine: This is pretty surprising, since getting an extra attack and an arc node should be valuable, but I find that I just can’t risk the -1 DEF and ARM, and Barnabas2 tends to be further forward than his arc nodes anyways
Gatorman Posse: They’re like bad Valkyries. They’re lower defense, they don’t help with guns, they take up way more space and they don’t hit nearly as hard or as accurately.
Bokur and Shamblers: They’re very corpse hungry, and very rarely tend to do anything since you’re going to sacrifice at least 7 of them every game. At ten points, they’re not much cheaper than sacrificing a Warbeast.
Blind Walker: Low defense, low mat, low pow - a boneswarm synergizes much better with the list, and I have never found a need for an arc node when my caster is in the middle of the army and all his spells are range 12 with Craft Talisman.
Minion Army - 75 / 75 points
[Theme] Will Work for Food
[Barnabas 2] Barnabas, Lord of Blood [+23]
- Blackhide Wrastler 
- Boneswarm 
- Bull Snapper 
- Gatorman Soul Slave [0(5)]
Dahlia Hallyr 
Orin Midwinter, Rogue Inquisitor [0(5)]
Wrong Eye 
Boil Master & Spirit Cauldron 
Farrow Bone Grinders (min) 
Farrow Valkyries 
Farrow Valkyries 
Farrow Valkyries 
Swamp Gobbers Bellows Crew 
I find that this list is really strong into combined arms lists, infantry heavy lists and battlegroup-heavy lists that don’t have the spell Synergy. I would explore something that is really good into Circle, Menoth and Convergence as a pair for him if I had the time.
In short, I really like Barnabas2, I think he’s really fun to play, he brings a lot of cool minion pieces and he’s surprisingly good into a lot of lists. Give him a try, he’s definitely way more fun than he looks.