Often going to be what you need from specific roles as it pertains to speed tuning, i.e. needing a 4 turn cooldown block debuffs champ at 4:3 

Sometimes will matter as to what champs you have for specific high end speed tunes, but also the champs you have available as you push the 2:1/3:1 teams. 

For slower comps at NM/UNM, those will often have Counterattack

But overall it is highly contextual and champ/gear based. 

Okay, I see. So if I don't have the high end gear for 2:1 or 3:1, the best option I have is a counterattack 1:1 team e.g. a Skullcrusher comp with champs that have 3 turn cds? That would be easy to tune, but it's no good if I want to do UNM and NM at the same time. Then I should build 2 teams?

No, you should be able to build a NM/UNM viable team in that case. What will matter is what you're building around the Skullcrusher, whether it just be a counterattack comp or unkillable with counterattack.

The cooldowns only really matter for the defensive stuff. Dps doesn't care about whether it is a 3 or 4 turn cd on their move.

True, I only need to worry about ally protection and decrease attack to be up all the time. I think I go with a traditional Skullcrusher counterattack team, 1:1, but I'll make someone else the stun target, I don't want to build my Skullcrusher that fast. Thanks for the tips!