Often I see people saying one must have a rank 3 Ghost, Corvus or Aegon in order to even bother with a legend run of the monthly EQ.  I’m here to tell you that’s a crock. 

I used 5* 5/65 Hit Monkey sig20, although sig doesn’t matter.  For synergies only, I used Squirrel Girl 5*, Venom 5*, Miles 5* and Electro 4*.  On the last quest of Master difficulty, I switched electro out for 6* CGR, to use for Psycho Man.  Any late stage EMs I ran into were dealt with by Venom or CGR.  I used 3 1 hour Champion boosts (30%) and around 40ish energy refills. 
This was my mastery setup. Hit Monkey strikes Guaranteed critical hits on his first L and both M hits. 

I used an iPhone 12 Pro Max, which is what got it for me.  Having zero load times between quests and even between movements and fights saved so much time.  
I didn’t screen shot my time but it was right around 3h15m.
So yeah, you don’t need 6* champs.  Just be fast and have a good device.  I wasn’t even fully boosted.  Best of luck to you all in the future should you try.  This was my third attempt.  First two tries were on an iPhone 7+, and definitely too laggy to do it.  Both were over 3.5hrs. 
Good luck
The SecretWarri0r