If you are going to run your supreme sorceress that way you would be far better served using Morathi. You get the choice of shadow/dark/death every game or a combination of both. You cast on average at +6 or +7 using dark and for what it is worth, she is better in close combat too.
Your other characters are setup quite well for survivability although personally I would like the Dreadlord to be more killy. Something like Giant Blade, Enchanted Shield, Dawnstone, Potion of Fools would be good here. 5 S7 attacks will take alot of things down. If you do this, charmed shield and 4++ ward on the BSB would do just fine.
In a 2800 point game, having only one scary combat unit is not going to cut it. Witch Elves will serve you much better than dreadspears, something to consider.