Ok so here is my T4 Venethrax list:

Warcaster:
Lich Lord Venethrax (+6)

Warjacks:
Seether - 9 (-1)
Seether - 9 (-1)
Nightwretch - 4

Units:
Bloodgorgers (Leader + 5 Grunts) - 5
Bloodgorgers (Leader + 5 Grunts) - 5

Solos:
General Gerlak Slaughterborn - 3
Skarlock Thrall - 2
Pistol Wraith - 3
Pistol Wraith - 3

Total:
35 Points (20 Models)

Tiers:
1 - Reduce the point cost of Seether helljacks by 1
2 - Place 3" AOE cloud in play at beginning of game for every unit in the army + additional rules.
3 - Slaughterborn and Bloodgorgers gain Advanced Deployment
4 - Seether helljacks gain Advanced Move.

Any observations and comments appreciated, models in blue I own already.

Seems like a decent tier list. 8 point Seethers are excellent, and will really help your focus loadout with their extra focus and Hyper Aggressive.

I would caution you to proxy some stuff to try it out, as you buy list looks quite expensive.