I managed to do both Darla Mavis arcs redside on my Necro/Dark Mastermind . The first took 26 minutes while enduring player debuff + no temp powers. And I got a ~5 minute phonecall in the middle. The second took longer, but I was doing it with no enhancements.
L24-29
Villain: Aurura Fades. 3 Missions. Kill 10 Longbow (plenty grays and greens nearby). Kill All Longbow +Click Glowie (Map is small). Take down elite boss (map is small island. Even without stealth it should be possible to swim around, avoid longbow groups, and attack boss directly).
Villain: Power Mine. 3 Missions. Click 3 glowies, each triggers ambush. Defeat All(Lost on smallish sewer map). Rescue and escort to nearby glowie (last mission may require travel to Cap au Diable.