Thief
If you want to avoid combat altogether and focus on looting as a solo player, the
Thief is the way to go.
The
Pickpocket Drone is an incredible tool, allowing you to scout or steal directly from other Runners who are preoccupied.
Grapple Device gives you the flexibility to reach vertical spaces and outmaneuver basically anyone but the
Vandal.
What holds them back is that their combat ability is very limited, so they're at a disadvantage in basically every fair fight.
Triage
As the medic class of Marathon, it's no surprise that
Triage wouldn't be as great in solo play.
While they do benefit from the survivability provided by their
Med-Drone, they can get outdueled due to their lack of mobility options.
While
Reboot+ can still be used offensively as an EMP, they have no use for their signature revive ability since they can't use it on themselves.
Recon
Just like
Triage, who is a powerhouse in teamplay, the
Recon can be underwhelming as a solo Runner.
This is because they are the premier info-gathering Runner Shell of Marathon, but info is only as valuable as your ability to act on it.
Not to mention that their
Echo Pulse is also seen by enemies, so it can be a detriment by self-reporting that they're in the area.
Lastly, they lack mobility and don't have offensive utility besides
Tracker Drone, making them a sitting duck in many situations.