Towards the very end, Ghostcrawler mentioned that skirmishers are "juggernauts with less armor" in response to the question,"Why is Ekko considered a skimisher and not an assassin?"
My understanding of the skirmisher class was that they're light, melee fighters with excellent sustained damage and combat mobility. I don't really see what they have in common with raid-boss juggernauts at all.
Does this mean that, internally, Riot is not in agreement on champion classes? Because his definition seems very different from yours.