Just started on Rouvy (we just got a Kickr) and I have experienced the same thing (4% grade feels like a 14% grade). I will adjust the slider in training mode this afternoon to see if that helps.
One question I have, I don't see all that many video routes available (maybe 15 or so in the United States, a bit more than that in the UK etc...). Is that because I am using it without paying (it doesn't say trial version but I assume that is what I am using), or is that what they have for now?