on the flip side, the BEST I have had is a 4* being at 5/8 at level 2/1.
I want to point that there is a huge food savings by leveling up 10 at a time, as long as your batch of feeders stop just before your hero levels up. This is due to the fact that the cost in food per feeder increases at each level of the hero.
So if you start your batch of 10 with your hero just shy of experience to go up a level (like 820/829 experience) the entire 10 feeders cost the price of food per feeder of the level stared on. So I always do batches of 10 until I am close to a level, then I stop just short of that, so that batch might be 9 or 8, then do another 10 getting as much experience into the next few levels as possible at the lower cost.
I think that this method would save A LOT of food over the course of leveling a bunch of heroes to max, and since everyone is always food starved, it does make a difference.
Does anyone see a flaw in this method?
For reference, the charts that indicate how much food per feeder per hero level was found at food calculator
Also, this chart is a good reference for xp per level per hero