Especially when 6th came out, a lot of people were discouraged by the newly added mechanic, random charge length. Many people point to how it makes assault units unreliable, nerfing cc armies. However, there are also some good sides to it. How has random charge distance changed the nature of cc units/armies?
Premeasuring allows us to decide just how far away we want to be from a given target. When you are playing a cc unit, how far away does your opponent come with his troops? Does he go for the safety of 18.1"? Probably not, but how close would you go? I think a lot of people see 16" as a fairly safe distance. The charging unit needs to roll 10 on his 2d6 to make it into combat. But lets compare this to threat ranges in 5th. A basic infantry unit had a threat range of 12". It was a sure 12" but it is still clearly less then 16". CC units in 6th make strong area denial units, because your opponent will generally prefer to avoid coming too close, even if the risk of actually getting charged isn't so big.
This doesn't mean that a pure cc list is epic winning, but a combination of cc threats and shooting is very viable. I'd say you generally want a cc unit that can still provide range firepower (shoota boys are hot in 6th). I tried experimenting with foot th/ss. It sure provides are denial, but is too much points for what it's bringing. If the cc unit has a larger threat range (jump infantry, beasts etc.) then It's even better. Perhaps then having a dual function as a shooting unit is not as important (e.g. spawns, wraiths, scarabs).
In a game where are control generally wins you the mission, cc units are still very potent. The nature of cc units has somewhat changed for sure, but in a supporting role cc units are important, and got a nice boost in 6th imo. On top of that, the new way assaults work in 6th are very interesting, and the assault phase is imo the most interesting one.