Hand of Guldan- The 'correct' way to use Hand of Gul'dan is to wait until there is less then 6s until you get 2 charges of HoG. You then want to use one charge, cast a few spells, and then clip shadowflame right before it runs out so you have ~5s of a one stack shadowflame, then 6s of a 2 stack
shadowflame. Doing this correctly will make Hand of Gul'dan out-preform Chaos Wave virtually always, and makes Chaos Wave pretty useless in PvE.

The damage of shadowflame is calculated upon being applied to the target, and not when HoG is cast. This means that you can enter meta after your second HoG, and shadowflame will be buffed with Meta.