Kill everything including crabs, but dont go out of your way to kill everything, speed = more runs = more chances than detouring from your route to kill 1 crab.
Use autoloot and get the LOOTFILTER addon and learn how it works. Setup a delete NAME filter starting with these :
Fish Oil
Lesser Mana Potion
Melon Juice
Murloc Fin
Mutton Chop
Raw Bristle Whisker Catfish
Shiny Fish Scales
Slimy Murloc Scale
etc
And you will save a couple of minutes per run clearing your bags of crap.
Add anything crappy you pickup. Set Lootfilter to autoopen clams etc. Keep the crab meat and claws, they sell for 10-40g a stack to people levelling cooking.
Be extremely careful using LOOTFILTER!
If you can take a main who can open chests, use keys, whatever... there are 2 chest spawns in BFD, 1+ will be locked and always contain a green / blue. I got 2 gruntblock shields from chests.
Pulling numbers out my arse that feel right from C.250+ runs of BFD :
a pair of wranglers every 3-5 runs, 1 perfect pair of wranglers that people actually want from every 10+ runs or so
a 'will be useless in cata' boe blue every 2-5 runs
grunts shield of something every 10 runs or so, 3 grunt block shields so far
Got 2x 5 stam wranglers from one run once.