Personally i really enjoy the 4set. Sure it's not always a raw hps increase because you don't always use the IoL charges. But on the later and harder fights augur/elisande/guldan mythic that i did it felt useful to have 2 big fol's. It simply provides more burst when you need it and otherwise it's just 2 faster hl casts. or hell sometimes i don't use both because i dps instead. Especially if you are doing anything below like 4/10 mythic i would advise to get the 4piece with like a heroic cloak and later on to switch back to the DoS. But that's just experience talking to hard math :P
And keep up the spreadsheet work it's nice to see.