The headline buffs in the v1.1.1 Apex Legends update were to make Gibraltar and Caustic more viable, by giving them 10% extra damage reduction to counteract their larger size, but it turns out the buff isn't actually working.
Gibraltar and Caustic are the two largest legends in terms of physical size, which in turn makes their 'hit-box' larger and therefore players using the character are an easier target.
This became a real issue shortly after the game launched, and resulted in many players turning away from using the legends, instead favoring smaller, more nimble characters like Wraith or Bangalore.
The new 'fortified' perk aimed to help make these legends more viable picks, with a health 10% damage reduction across the board.
However, the new passive perk was found to be bugged shortly after the v1.1.1 update, as players started going back to Caustic and Gibraltar.
Due to the bug, players health would begin to drop if they took damage, even if they had a shield equipped, whereas the shield should of course deal with all damage until it is depleted.
Thankfully, Respawn's community manager Jay Frechette has confirmed that the team is aware of the issue, and working on a fix.
In response to a post detailing exactly what was bugged about the Caustic and Gibraltar after the v1.1.1 update, Frechette explained the fix was currently being 'tested'.
Unfortunately, Frechette doesn't give an 'ETA' for the fix, so Caustic and Gibraltar players will have to wait a little longer until their big legends become more viable.