I just did the black spindle bonus extra in a destinyLFG pug, its insanely hard we finished with just 22 secs left. I'd recommend everyone be at least 295 light, use your swords for the first two rooms and then rockets for the third room. Killing the boss stops adds spawning but you have to clear them a bit or they overwhelm you fast. I got the 310 sniper rifle Black Spindle which is basically black hammer 2.0 and a legendary ship. I don't think anyone is going to be soloing this anytime soon, its really an insane amount of 290 or 300 mobs in the final room and there is nowhere to hide. I did it with titan (me) as sunbreaker and two golden gun hunters, I think a 3x titan group would be the easiest since you can put up a bubble and have the other two go sunbreaker.
Its really awesome bungie is putting in tons of hidden stuff like this, there are probably more in daily story and strikes to figure out
the easiest way to do the 7 orbs quest is to do undying mind strike, there are 2 areas where a TON of yellow mobs spawn. The first is right before the first "boss", just go nuts but be sure to aim right so you are hitting at least 3 yellow mobs. The second area is the boss itself, when he is at like 75% and 50% health he spawns a ton of yellow mobs on the left and right sides of the rooms, just go nuts there. Its really only hard on a warlock, the other classes have much easier times fulfilling the quest terms. You can probably make a fireteam on destinyLFG to just do the quest and run that strike. I wouldn't do the go earth patrol way, if you wipe in a strike you get pulled to the team so if the other 2 people die you get teleported away.