I multileveled the 6 hardest hardened levels when I was at the start of Stage 2 (9k total AP). People called me crazy, but even if it took me 4 months, it would be faster than my current pace. result ended up being that i completed it in 2 days. Took me 4 months to get 9k ap and then 2 more days for 26k AP

Reason I was so fast is that there are a LOAD of IM powers which you can superpower on there, Save up some powers first, and get good information on the best merc camps, and you should be set like I was.