First of all I would to point out that comparing the Forge to the year one Nightfall is not fair. If that's still how the the Nightfall worked that would be one thing. However the Nightfall no longer boots you back to orbit when you wipe. Bungie changed that because they felt it overly encouraged playing it safe. Moreover I personally think your argument only makes sense if the rewards were greater if you soloed it, which they are not. A solo player has to deal with the same enemies in the same amount of time a group does, but without the benefit of being able to die like a member of the group can. Also as an aside. I have almost never seen a group of players wipe at the Forge. It is absurdly easy to just wait in a corner for everyone to spawn back in. If they do fail, it is due to time out.