I agree with Mitch, the cauldron does the same job, can do it to multiple units, can do it for multiple rounds of combat, and can choose to ad KB or ward save instead of attacks.
I would however want to keep a cheap BSB in the army, since BG goes from a 1/6 chance of breaking to 1/36

.
I personally run my BSB on foot with 24 spearmen, it makes for a very vicious unit, with a grand total of 6-7 CR.
The BSB I would recomend is: master, bsb, gw, armour of darkness 134pts
They really should have shields IMO, it does make a huge difference.
I would personally go with CD rather then null talisman, it really is incredibly powerfull when combined with ASF.
I much prefer the knights over a hydra if he do get a cauldron, the +1 attack is really deadly, I would howver prefer a naked unit, i.e. five with no upgrades.
I personally don't like her, IMO; a single level four is not a sound investment unless you get either the black staff, or sacrificial dagger.
I do understand why he takes the focus familiar, it is however possible to either scrap the ring, or to simply keep her more then 12 away from it.
I am not a big fan of bolt throwers anymore, not with our improved crossbows, I would much rather have 10 crossbowmen with shields, and five shades with GW's then two balista.