Allrighty, here are my thoughts:
Regarding characters, the doombull looks fine (not that he has many options anyways). He could have
MoK, but that would change the dynamics of the list quite drastically. The tricky parts are the chariot-mage and the demon. Altough the exalted is quite expensive, he's unfortunately not too great in melee, so I'd swap the ward upgrade for soul hunger, so he's more reliable in taking out the light stuff. Due to his great mobility, you can dodge most magical attacks with him anyways. The level & scroll are debatable, but I can see getting some spells if you're against only 1 scroll caddy or somesuch (and the added magic defense sure helps). Mages in chariots are generally not too good an idea (unless they are goblins bearing "gifts"
), as that will put them into harms way when you're more often better off just blasting away from the distance. I'd swap this guy for bray shaman equipped with lvl2 upgrade, 2xscroll and a braystaff and get him couple of cheap beast herds for bodyguards and for supporting the minos. If you want chariots, pair of tuskgor ones are quite a bargain.
Regarding the minos, I'd wield at least 1 or preferably 2 main hitter units which are 4 minos with banner. The smaller can't take ranked infantry head on for example (and getting multiple charges off on one target can be tricky sometimes), so bigger units with added combat resolution should help there. Couple of cheap herds would supplement these guys well.
The Shaggoth is pretty meh, especially in this list which has loads of heavy hitters already. He lacks the neat tricks of a giant (altough he has decent armor save to ward off light shooting).
Tbh, I'd just take some support troops (chariots, herds, spawn etc.) with the 300+ pts.
