After getting max class

[Mr.Peso]

Btw anyone has an idea of what is required for hero classes?

Because when i'm at 150k xp of melee i would like to put it in ranged to increase my agility, but i'm afraid that it will slow down my process of become the legendary class

Till youre lvl 52 you have around 987k xp, plenty to spend in both ranged and melee.
Besides that you only need like 80k ranged xp to get the maximum of 30 Agility.
Putting assist xp into ranged gives you slightly less (0.4) than in melee xp (0.5)
but at the end it's not a very big deal since your gonna spend a lot of time on your char to grind stuff.