He's an odd mix of anti-magic and brute force.
I think you have to be a crafty player to use him well because his
base size makes him easily exposed. However, he does have a
few advantages over the Feoras (though maybe not against them
due to Immunity Fire).
1. Reach. Even though he's slower, Reach gives him the ability to
attack past models in the way if you can draw
LOS to the target
in melee. Feora1 can only attack in .5" However, Feora 2 has both
Reach AND a self teleport spell, but she loses Engine of Destruction.
2. Witch Hound. What's every
eHaley's favorite spell? Telekinesis.
What about Aiyana and Holt? Harm (or whatever it's called now). How
about pDeneghra? Crippling Grasp. In Menoth you can create a
dilemma with Reznik and Choir. Make it no spells or make it no shooty
and count on the enemy to not want to cast spells. Of course, making
use of Witch Hound means your enemy is forgetting or thinking
the trade is worth it.
3. Movement.
eFeora gives her Warjacks extra movement. pFeora
turns them into auto-hitting infernos for a cost of 4
foc. But Reznik
cancels out one of Menoth's glaring weaknesses. He can grant Pathfinder
to a 'jack. I think only Amon can do this, but that's Amon. In addition,
the 'jack with Iron Aggression on it gets boosted melee attack rolls. The
problem with the tactic is that they can see it coming. Who cares?
Maybe they'll cast a spell at that 'jack
In addition, Perdition gives him an offensive move his warjack around
option. Not the worst thing in the world to have.
4. Anti-magic: Purgation on himself is amazing, but it's also dangerous. He
suddenly can get boosted P+S 18 attacks against a target with an
upkeep spell on it. Be careful, he'll be exposed at that moment, especially
if you cast Engine of Destruction to get P+S 18 attacks (equivalent
to a 'jack, in case you're wondering where that falls on the power
scale). If you do hang out Reznik to dry (and it will be easy to because
he can charge 10" and reach out to 12") you have to use his feat.
Judgment Day strips fury and focus and prevents focus allocation
and upkeep spells. If they're running 'jacks, they'll have to rely on the
warcaster to finish off Reznik, and they'll have to re-cast any useful
upkeep spell that they want to use against him, lighting them on fire.
If you're playing against Hordes, however, the warlock will be starved, but
the 'beasts will be able to force. So be careful.