Classes with less health, should have more gear, not more perks.
Scout pred should have more utility to make up for his health shortcomings
Berzerker pred should have more perks, as he is focused more on damage dealing, and melee, perks would be better suited for him.
same applies to fireteam
If you want an in game reason. Lighter armor would allow for more utility as they have more weight that they can handle, heavier armor leads to less gear, which forces skill (Perks)