First of all, the forge is not meant to be a solo activity. You just need to make sure that when you enter it that you do not run or ride a sparrow. Walk slowly. This will give the matchmaking mechanic time to get you into one that has other players in it. Second. You have plenty of time to complete a fused and enhanced solo. You have to be mobile and use the various points of cover to your advantage. Also be sure to shoot and destroy the siva cluster that spawns in the dome when your worth is being tested. Then be sure to grab the ax and use it.