the big problem on treachery is, without that fate proc its garbage...
imo best combo with cold sunder is:
act2 prayer merc, eth elite cure, eth elite coh (eth upp'd um'd 7ll "skin of the flayed one" will work too, if u can get a cheap one to dodge the ber rune for coh)
without cold sunder i would go for act2 might/holy freeze merc, eth "andariel's visage" at least ral'd, if no ias/fr jewel in hand and eth elite forti
non eth variants are good too
for cheap:
tal mask or cot or 8ll gaze and griswolds armor socket with ral, ort, tal, thul (cot already have fire res)
always have the life pool from merc in ur eyes, to give him pots with short keys or tele back
if u want a tanky merc just as a blocker and u can give up insight, full sazabi act5 is great
Think I want to dodge the ber for now… so best option is upped flayed or a griswolds? Using griswolds atm with a tal ral ort