I have read the forums alot but the main information I used because of their incredible success at multiple Signet drops, was Cuckoo gaming video's (not associated with them). They often concentrated on shorter faster runs getting the stacks fast in the Black Canyon Mines and Road to Alcarnus.
Here is my route:
- 5 stacks in Vault of Assassin (apparently a very low chance it will drop here, start here from waypoint of previous session to save alot of time).
My reasoning behind this is you can have the maximum run length and maintain the 5 stacks longer for the more useful areas that have been more often known to drop the Signet. Legendaries don't often drop before 3-4 stacks and these stacks can be maintained very quickly here and are guaranteed. No other areas besides the Oasis itself can guarantee 5 stacks quickly. On the Cuckoo route sometimes even after going to 3 different places I would only have 4 stacks once entering the Sewers (best place for signets). This happened despite adding the second sewers next to the Oasis for it's 1-2 elite packs. It was inconsistent and frustrating and the Vault is faster. All these areas can drop Signets.
-Black Canyon Mines
This area has up to 4 elite packs in one tiny area, you'd be insane to do a run without it.
-Road to Alcarnus
The first area after the bridge only, can have up to 3 elite packs and can be cleared in less than a minute.
These areas all drop the signet and likely have higher potential to drop it than given credit for. They naturally won't drop it often if you getting your stacks there. It is also low enough level that the Manald Heal may never drop forcing the Leoric ring instead. Within the first 2 runs I started this new route I got 3 legendary drops from these areas.
-Ruined Cistern sewers at the Path to the Oasis waypoint.
If you find the second elite pack early just exit right there and go to the Oasis for shortened times between packs.
-I go to that waypoint again and start on the Oasis itself.
I often don't use the next waypoint spawn within in the oasis itself because it's location is inconsistent. Once you find The Forgotten Ruins you can go back to this same waypoint and simply run in the opposite direction you did on the first try to clear it (if you don't finish the Forgotten Ruins with a convenient exit near you).
I clear the whole oasis to make the run as long as possible and keep those elite packs coming. To me starting over often to get 5 stacks is a much bigger waste of time, the reason I find all the best areas in the whole act to farm for it. I often only clear normal monsters if they are in the way and try not to use extra time to kill them (anything near dies instantly with the Mantra of conviction and Tempest Rush) unless there's a hoard of them.