Legendary quests are available only to the legendary classes

[Kriegstofu]

i think he means quests for different heroes. for example:
XBow Heroes: kill a lot of Ranged Bots (80% Ranged 20% melee bots)
CM: Kill some Inf bots aswell
AV: Kill some Tricksters/Assasins Aswell
PC: Take x Damage/Repair Shield 1000 Times

Inf : Kill a lot of Melee Bots (80% melee 20% ranged)
Skirm: Kill 60% melee and 40% ranged
Archer: Kill 60% ranged and 40% Melee

As xbow is most accurate/shoots the furthest i think it is specialized to kill ranged, as bow has less speed and jav even less.