For point of reference, I have three 
champed (thing, deadpool and X-force wolvy). All of the five stars I have remain at level 255, because who needs that headache. I just got a red OML, bringing me to 1/1/1 on him. Is it worth spending the ISO to level him up?
I’ve got over 200,000 ISO. In theory it’s be saved for leveling up
Hawkeye for farming purposes and and hulkbuster whenever I got that 13th cover (or Elektra or Invisible woman, but less exciting). But who knows when the latter will come (and mine is at 195 so it’s not like I’m going from 70 to 270).
I get my OML yellow from resupply in 11 days to take mine to 4/1/1 and after getting some feedback in the Roster Help forum I fully intend on levelling him to 345.
I just opened 7 LTs and 10 Classics in the hope of bringing some of my top tier 4s closer to max covers so that I could invest in them instead but I had terrible luck and pretty much drew stuff I had no interest in. My 4 transition has been slower than a stoned sloth and I need something to keep me interested; beefing up OML is it.
You almost are going from 70 to 270 - it’s about 260K to go from 195 to 270.