In 8th I usually go with something like 9 or 11 IC/reiksguard for my hammer units. Rarely bother with regular knights, when I have two units that have acess to S4, I'd have to run a fully mounted list in order to need the normies. I also never take more as they become too points heavy. These dudes are for flank charges and in general cooperating with my infantry units who act as anvils.
I don't think I've ever taken a captain with them (maybe a BSB once or twice). I don't feel like he contributes to the outcome of combats that much with his puny 3 attacks. I also don't feel like I need Hold the Line! They are not foot troops, they aren't meant to take a beating and pin the enemy in place, they need to choose their fights and punch through. If I'm rolling a break tests with them it means that I have already goofed real bad and probably the battle isn't going in my favour. Kinda like giving banners to missile units - if you're in combat with them, you goofed and that stick is not gonna save you!
But they absolutely NEED a mounted Warrior Priest, to mitiagte that rubber lance syndrome. The unit only has 10-12 attacks, you need these to strike home in order to do anything, hatred is necessary. The prayers are just a bonus, if you get them off - good for you but don't count on it too much.
EDIT: I should mention that even though I don't take normal knights for hammers, they are of course perfect for small 5 men units to chase away enemy chaff and go after shooters (the so called "Vanilla Knights").
