I've done Positron a couple of times... there are some decent guides, but they're mainly useful for giving you and idea how much you have left to do.
The first few missions are front-loaded and hard (esp. for large or careless teams) but you can stealth to the objective if the team has that ability.
After that, it's annoyingly like doing a long string of regular missions without being able to switch contacts or go shopping. It's not until the final few missions, where you start running into multiple types of mobs inside, that things get vaguely interesting again.
The first few missions are front-loaded and hard (esp. for large or careless teams) but you can stealth to the objective if the team has that ability.
After that, it's annoyingly like doing a long string of regular missions without being able to switch contacts or go shopping. It's not until the final few missions, where you start running into multiple types of mobs inside, that things get vaguely interesting again.