I have no problem ever soloing the Forge.
But when I do die it's always because of one little thing. THE EXPLODING SHANK!
Every single death when I'm solo is because of those stupid shanks. It's the only enemy you need to worry about and I actually only complete perfected offerings about 50% of the time when solo simply because one of them is going to get behind me at some point and explode.
I hate them.
No prob. My favorite location because you can shoot at all areas from up there and clear that tunnel that opens easily, especially if you have solar grenades or smoke and void grenades.