I also failed with CryEngine two years ago at asset import pipeline which is apparently remained similar. and messing with Lua and xml files made things even worse.

UDK was not an easy tool too, but UE4 is much easier in every aspects. okay its C++ related docs is not full and not good, but you can always jump into the source (at least headers are well commented), and you can find plenty of information and help at the forum or answerhub or wiki. After a few months I started to understand and really love the way how you can make the core in C++, then expose things to be editable in the editor, or access from Blueprints, and only if needed...