Two things:
One: a the legends are balanced based upon internal performance statistics. The goal that the devs have said to keep I n mind is that legends should perform well in their intended role, and that complementary teams perform well across all mixtures.
Two: The original legends are remixes of Respawn’s pilot kits.
We have:
Mirage: Holo+Cloak pilot kits
Wraith: Phase pilot kit
Caustic: Reskined thermite/scorch kit
Bangalore: E-smoke+situation stim
Pathfinder: Grapple pilot
Gibralter: Dome shield+A-Wall
Lifeline: Particle wall
Bloodhound: Sonar pilot
Each of these sets have been re-balanced to compensate for the mobility decrease from Titanfall to Apex.
For instance: Bloodhound’s ability, in Titanfall, provided minimal alert of a scan, along with no indication of the direction. With the pacing in Titanfall, this made sense since pilots could rapidly reposition.
In Apex, most legends move significantly slower than a pilot in any situation. Thus, Bloodhound was given the counter of giving away his position. This allows teams who are scanned the time to reposition to defend. It also indicated which directions to flee if need by, via process of elimination.
Additionally, there are several legend specific-counters. Mirage decoys obscure vision and add extra “noise” to distract. Wraith gets an early warning simply from being looked at. Caustic and Wattson both possess area denial skills that can rapidly be deployed. Bangalore can utilize smoke to neutralize the boons of Bloodhound to their teammates. Octane can rapidly change locations like pilots in Titanfall could, making the old scans worthless.
Additionally, assets such as arc stars or thermite grenades can slow or block passage to rushing opponents, buying valuable time to implement your squad’s favors tactic.