I think most canon fighters mount only about 1/3-1/2 their maximum armor, making them a bunch of flying Shadowhawk 2Ds or Hellbringers.
I don't think they were designed that way though.
Most are fine if you have the same tonnage in armor on a mech of the same size.
SparrowHawk mounts what 7.5 tons on a 30 ton frame? That's more than a mech of that size.
IIRC Fighters didn't have a Maximum Armor till TW.
Which would have been fine but you have this oddball from back in the day, Lucifer-20?, that had INSANE armor for its size.
So when they came up with rules for Max Armor they had to account for that one ship.
Which now means everything else is "low armor" but its not really.
If a ship is mounting 10-13 tons of armor at 65 tons then its right in line with a Catapult/Thunderbolt.
No one expects a design to turn around and mount 20 tons of armor on a 65 ton frame.
The Luci only pulled that off by being VERY slow for its size & also under gunned.