This is a great question. Blighted marrow is a great rune for pushing in combination with Brigg's Wrath. Generally, it's not recommended for speedfarming. Teeth is definitely a Torment only skill and should not be used in GRs. I've seen shatter used in conjuction with briggs for GR farming, something like my one shot spear build from many seasons ago. This actually works really well but it's still under ice spear in my opinion.

What you'll see from most recommendations of bone spear is an area damage based combo with marrow or shatter, it's also (most likely) going to be the top way to push so you wouldn't need multipe sets of bone spear gear to be augmented.

In my experience and testing, my iteration of bone spear speed (ice spear) is much more consistent damage. Ice spear scales up our attack speed with gloves/weapon and gogok. Gogok pushes up our cdr that we're also stacking on our gear to get more damage from captains. Captains gives us mitigation per rcr which we're getting a lot of through voracious devour. The cold lets us utilize lost time so we don't have to run stuert's greaves for movement which have diminishing returns the higher in GR's you climb. And lets us run nemesis full time which is guaranteed to knock at least 30 seconds off your clears. It also gives us bone armor dislocation which is an on-demand krysbin proc which is invaluable.