At higher levels, it's difficult for any class to solo missions. There are exceptions such as an Agent with 1600 conceal or a Fixer with Grid Armor. But in general, you have trouble doing 50% missions. At lvl 70, I was doing 75-80% missions and all my armor came from mission rewards. At lvl 102, I need to do QL 150 missions to get armor I can use. I can't solo them. However, if I get a well rounded group, we can get some really useful things.
For example, as an MA, I tend to use Str/Agi armor. Soldiers and Enforcers typically use Str/Sta armor. Agents typically use Sen/Agi armor. NTs, MPs use Nano or Cyber Armor. Docs use Biomed Armor. And so on. Now that MOBs are dropping items of their level (same as chests), it's more effiecient to run a single mission with a team getting useful items than it is to run three or six missions at 50% getting crap that you can't really use. But selling them so that you can buy stuff that you can actually use.
Soloing's great at lower levels, but it becomes increasingly difficult.