It really depends who ur playing against. I assume ur playing against Sphess Mahreens so here are a few suggestions
Dark Reapers- Necessary. Wound on 3, ignore most armour saves. Brilliant unit, but only use them against SM
Howling Banshees- Also Necessary. wound on 5 mostly, So use a farseer with doom, and wave serpent so they dont die. Upside is they ignore armour with power weapons!
Farseer- Love hate. But the powers make up for it. really pay off on the battlefield