I actually think the Rebel large base ships have it pretty easy against triple Scouts, in that they can do a really good job of controlling range. Where they tend to suffer is against Aces who are moving after them (Soontir/Whisper/Vader). In my regional event I ran Dash/Lothal Rebel and didn't have any issues with Scouts or the Whisper/Echo list I played against.
Umm, that's all well and good but the topic of this thread is 4 Ship Rebel builds......... (ie small ship Rebels)