lets compare this areas:
Plaguelands:
- easy to farm with almost every class
- no immunes exept physical
- stitches can drop divine gem
- good drops overall
- drops infernal chest
Inferno portals:
- mobs with multiple immunes, stronger, you need to be very good geared
- people is running only 1 portal, because summonners are too annoying
- bad drops compared to plaguelands
- drops infernal chest
So, i dont see any point to farm inferno.