In the unmodded game, the window of opportunity is too low. You cant use them to clear barbarians effectively...because while warriors get the first +7 strength promotion easily, the scout gets nothing. Every battle leaves them damaged and needing to spend 4+ turns to heal back up in the ancient era which only costs 40-60 turns. The extra mobility isnt as big of a deal as IRL beause you cant even get flanking bonuses till you get a civic, and ideally you want to boost that by clearing a barbarian camp first. And flanking is nowhere near as powerful as it is IRL compared to the easy +7 strength promotion that the warrior gets.