Farming Leoric's signet.
Why? Cheaper to get paragons level then upgrade my main gear (3dx, 2vit, 1int, 1str, 3mf, 3gf per paragon level):
Total exp to paragon level 100: 10454400000
My current exp per hour using helm with red gem: 12000000
Total necessary play time to paragon level 100: 871 hours
Total estimated hours to paragon level 100 with Leoric's signet:: 711 hours
Current AH price: 20M for a crap one, 40M for decent, 100M for the best ones, don't expect prices to be lower 'cause there is one flipper buying cheaper ones and re-listing.
So, even if take like 24 hours farming for me I believe it worth a try (I can't make 20M farming 24 hours ).
Current MF with 5 NV stack: 351% (300% with 5 stacks when I found the ring, I wasn't full magic gear)
Route 1: VoTA, sewers, cistern, oasis - full, desolated sands - surface (sometimes I try mines and starting from a royal audience up to VoTA).
~Total hours of farming: 18
Status: 8 legendaries, RING!!!!
RING PLACE: act 2 normal - Ruined cistern - orc pack.
Aquila Cuirass - Armor req level 15 - Oasis
Pox Faulds x2 - Pants req level 9 - One found at mines
Do not remember where I found these
Vigilant Belt x2 - Req level 5
Broken Crown - Helm Req level 16
Magefist - Gloves Req Level 16
Case in point!
Just found a 26% signet, FINALLY, with a 3 stack NV inside The Ruins Level 1 of the Stinging Winds (west, before Khasim Outpost), off of a Stinging Swarm mob, reported as level 18 by d3db. Normal mob (not champ/elite), 304% total MF at time of drop inclusive of 3-stack (<--- this is what complete data looks like). This is my ninth legendary (first ring) doing this targetted farm.
For those interested, my run is pretty comprehensive and starts with the Lieutenant Vachem checkpoint of the Road to Alcarnus quest, runs through the black canyon mines for a quick 2-3 stacks of NV, then through Stinging Winds (west) to check for Ruins and do the center map tile event, then Khasim Outpost, Stinging Winds (east) to check for Ruins again and also do the center map tile event, Road to Alcarnus, Alcarnus, Audience, Sewers, Cistern, and finally Oasis (including both Tomb side dungeons and the one cave full of the ghost mobs, if any of those spawn.)
Edit: Knowing this, I would be comfortable now adding The Forgotten Ruins at the end of my route, since the skeletal sentries (archers) and bone warriors inside are level 18, and there are many. I'm also pretty comfortable with this run because it is less monotonous and runs pretty much the full gambit of level 17 *and* level 18 mobs. :D
I'd also like to drive home the value of checking for The Ruins in the Stinging Winds. It is entirely snakes (17) and locusts (18). You can ignore the pillar spider spawns (22). :D :D