Personally I watch videos twice ot thrice to learn serious fights so that I have a general idea. Then with practice and repetition (because you are going to repeat end-game content). There is no worry about learning 2.0 content as you are not likely going to replay the 50 instances ever again after you are done with the 2.0 content (which you can easily get carried through by unsynched players.). No need to feel worried as the only content you really need to remember are raid and EX trial ones as everything else is very forgivable.