My issue with the game is that the games generally feel very one sided. Either your destroying, or getting destroyed. There doesn't seem to be much of a middle ground, at least in my experience.
I feel like the need to focus fire one of two fires on a specific, priority teammate makes Mercy slightly fiddlier for a complete new player though - just from a perspective of getting going with the game. I also feel like people are really *really* bad at looking after their Mercy right now. That'll change but I feel in the random queue Lucio provides a little more self-sufficiency - for now at least. I'll probably give this guide another pass in a month or so when the community has thinned out between Quick Play (which newcomers will likely gravitate towards) and Competitive Play.