So thanks to @NightCrawler9 i found some plans getting 5 stack from canyon/road/sewer in act2 and then killing kulle
then i thought, ghom is a quick wp away, so let me do skycrown/keeps3/keeps2(if necessary) and then kill ghom

this was working ok, on mp7 for both DE and plans, but then i read this thread over at reddit, and i wanna try it out

Heart of Sin, Second Heart
Circle Tower of the Damned Level 1
Kill Cydea
Kill Azmodan
Kill Iskatu
Kill Rakonoth

i think plans will drop in price since they're dropping fairly easily, so farm them while they're hot!

We've discussed this more than once. Yes, that is the most efficient route. There's evidence that Siegebreaker also drops plans if you're getting bored and want to extend the run further.