Summoning most things are useless unless you can get at least 2 of them off a turn at which point you are spending a fair amount of points, T3 5++ its really easy to kill, and a herald cannot join a unit until the next turn so in most cases will just die. Granted it takes the firepower away from something else but certainly in smaller you aren't going to get that much. Bloodcrushers may be useful T4 W4 and you get three of them so ho know with that but most things aren't going to last, especially with the ridiculous amount of dice you will need to do it.
Me: To be honest im amazed there isn't a chaos god of not revising or at least chaos god of procrastination
MidnightSun: There will be, when enough people do it. Y'know when the Eldar were all engaging in their hedonism and Slaanesh ripped open the Eye of Terror with his creation? Slaanesh will have NOTHING on the God of Procrastination, and his vile minions will carve the galaxy asunder in a thousand year reign of blood.... Tomorrow