It really juts boils down to:
HARD
There are some people who find it fun to fight villains that are higher level than themselves, for various reasons. They get more xp per villain.
EASY
There are some people who find it fun to fight villains that are lower level than themselves, for various reasons. They get less xp per villain. However they will (probably) kill at a faster rate, and hopefully make a comparable amount of xp/hour.
So if missions are marked with a difficulty, then people would be able to choose the difficulty of their mission.
If the difficulty is chosen via a slider, then as long as the slider can't be adjusted in mid-mission to make one particular foe weaker, then that's okay in my opinion.
If the difficulty is just a field in the mission description when you choose Mission A or B - as in Mission A(easy) Mission B(hard), then that would be all right as well to me.
Just have the difficult mission spawn the mobs as +1 compared to the regular missions.
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I started a tank to see the lower levels again, and it's a lot of waiting around for myself to heal up before I deal with the next +1 group in missions. I know it's a bug, but I still have to say that +1 means a lot of downtime between fights for him. +1 at Level 5 is Level 6 villains - you could say the villains are 20% higher level than my hero! hehe.
Upsen.
