I’ve done it single player on normal and hard. It is a difficult mission, yes, but it can be done. Timing is essential. Change yourself to the objective class, and do it incrementally. Repair the crane whenever the coast is clear, eventually your team mates will be there to defend you. Be absolutely sure to stop repairing and start defending if you get shot. I recommend a heavy type with a Hjammerdiem and an AR, and to get yourself as buffed as possible.
For the hack, clear out the area with your team mates, and play it safe. Try not to die. Once you clear the area, stick the hackbox on and run for cover. It might go down to 3 bars but it’s ok. With the cover that area has, you’re never too far away from the hack box. If you see it go down, retaliate with the shotgun as fast as you can.
Golden tip: Grenades are your friend! Use them a lot!
Also, turrets are a big issue at the hack box. I recommend using the hack turret ability for your Operative.
Hope this helps!