The difficulty is determined by the person to whom the mission belongs. In the mission window, beside each person's name is their current difficulty setting.
So, if the leader picks Capt. Crunch's mission and he is set to Rugged, then the mission will based on the level Capt. Crunch was when he got it and then modified by the Rugged setting (which is normal sized groups of +1 & +2 level villains).
1) Once difficulty has been set, all your missions spawn at that new difficulty, regardless of where they are instanced. I had several in PI last night, but a couple took me to Skyway and even Boomtown. All spawned at the higher level.
2) The mission spawns at the level of the mission owner....so everyone fighting with you will face the same critters you will. Mission sliders show no mercy!
3) You can move it back down a notch...but it costs you each time you move it up or down....at my level, the price seems to be the same to go up or down a single level.
HERO CORPS FIELD ANALYST LOCATIONS
Atlas Park NE of Atlas Plaza dot, opposite of Henry Peter Wong contact (-40, 15, -885)
Brickstown Standing next to hospital, close to Neal Kendrick contact (?, ?, ?)
Galaxy City Out back of the Freedom Corp HQ (?, ?, ?)
Independence Port On hill, across street from hospital door (-1565, 5, -5500)
Kings Row Near Blue Steel trainer (?, ?, ?)
Steel Canyon Opposite side from Positron (-3135, -80, -395)
Talos Island On the base of the Talos statue (1715, 13, 7745)
Skyway City E of Tram station, in small park area with Minx & Synapse (-70, -25, -5115)
Founders' Falls W side of fountain in Williams Square (3890, 0, 600)
Peregrine Island At Portal Corp sign (-1500, 0, -340)