Little Daemon Boy? Have you SEEN the new model? It is in no way little. Paint it right, it's down right intimidating.
And why are you throwing a Seer Council at a Daemon Prince? Lets, see.... They have at most 2 attacks (unless charging), and the Daemon WILL get his 2+ save (most Daemon's are given this upgrade). It just so happens Daemon's can get dreadaxes! Re-rolling your saves will get you....... nowhere.
Ghosthelm's are great and all....
But the Daemon is still hitting on a 4+ (5+? where'd that come from), wounding on at least a 3+ if not a 2+ (if its got daemonic stature and strength), and if it's a slaanesh daemon, then your in trouble, because its going to be getting shot up on drugs and lowering your initiative.
I don't deny that in some situations, the seer council can be good, if not great in close combat! However, throwing them against a Daemon Prince (who is likely to be somewhere around 20-50 points cheaper than your council, when he is fully pimped) that will chop the council down, is not one of them.
Now, the ghosthelms and HtH council should do fine against the smaller daemons, especially now that their invulnerable save CAN be rerolled.