In legends I level all my warriors below the 100's up through Training Dojo. The lowest are at 87. When you reach the 100's it cost more rupees to level them up. Like way more rupees.
Personally I don't find MQ map that hard. Yes it has some ****ty levels like the Don't get hit missions but you can beat it with low leveled warriors. I always got the rupee+ skill on my weapon. I like to level up warriors I absolutely don't care about through Training dojo. And I'm always...