Mob levels are based on the overall power of your mods on your gear. Newbie 1-20 will have low end mods that might have 1-2 points and maybe some silver mods. 20-40 they expect you to have higher ranking in your mods, so an example be serration where it should be power rank 5-9 which is almost 100% more damage to your riffle. Adding in a few of the more rare mods like streamline and flow on your Frame help make your skills cost less and more of a energy pool. 40-60 they expect you to have a good chunk of maxed mods and good synergy going with them and maybe even formaed a few of your pieces of gear. Everything above 60+ is making sure you are putting in the best, maxing out damage mods, knowing how to make elemental combos on your weapons etc. Only time you will see 60+ is sorties.
Sortie 1 is 40-60, 2 is 60-80 and 3 is 80-100
Sortie 1 is 40-60, 2 is 60-80 and 3 is 80-100