That's why I plan to stick with 7x3 skullcrushers max, maybe try out 6x3 and 1x6 units because I have 24 skullcrushers total. I had enough points to also have 2 slaughterpriests, 2x10 bloodreavers, and 2x5 wrathmongers. Typically the bloodreavers run up ahead of my skullcrushers fo eat the enemy's charge and die to trigger the charge bonus. With units of 3 I usually don't have an issue getting them all into combat. Even with the extra units I still have difficulty protecting objectives when there is more than 1 or 2. So far I have faced armies that the skullcrushers can tie up in combat so I don't have to leave too much behind but I would imagine armies that can teleport or otherwise get past the skullcrushers would easily take objectives from my list.