I gather in Warmode, Revendreth. Along the route I take, using Gathermate and FarmHud and a Druid/Sky Golem I'll get together ca 200 Widowbloom in an hour with maxed out herbing.
That's without counting Nightshade and Death Blossom, but those do add up to a nice sum as well. I always shoot for at least 200 widowbloom from each farming session.
Widowbloom sell for 36-37g a piece on my server (Draenor EU).
mining/herbalism in zereth mortis is quite profitable for me. I can farm arround 20k/hour in Kazzak unless im super unlucky and dont get any progenitor essintia. Im farming on druid with jiro buffs. never tried other zones.