its also auto hit, instead of sometimes missing

that part about leveling takes long is only partially true...

even though the normal mercs start at a lower level, they require less experience to level, so when you get into the 90's your normal merc might catch up and over compensate : )

i'm sure theres some kind of linear function but it's not too important considering it takes a character to get from lvl to the next harder compared to a merc