okay solution to this.. on console: go to settings -> date and time -> set manually - set clock to somewhere in the past -> return to game -> load into patrol area on mars -> see if you are alone in the roster - if alone start escalation protocol - kill thralls / perfect point to do banshee 44 bounties.. -shadow rift apears , change to other patrol area - repeat - - finish.. this is how you fast grind such "kill 2 billion enemies" bounties without disturbing or wrecking other peoples experience since you will be the only one in this instance anyway.. have fun.
I just grind the kills in the Thrall pit in the Whisper mission. You get 15 minutes of constant thralls rushing you, so you can just stand in the cut out section at the far end with a Huckleberry and you don't even have to move or reload the entire time. How to grind it out isn't the problem, it's the fact that it seems so excessively grindy compared to the other kill bounties that he offers.
well i do not consider those "kill 100000000 enemies" "bounties as a good way to do this.. reminds me of the last MMO i played "silk road".. oh.. wait.. destiny wants to be more MMO-like.. well .. there you go.. prepare to get someone 1000000 shank butt-plugs to banhsee.44 which drops every 10th shank. yeeeeeeeeee