The new Apex Legends update on March 23 made changes to the Heat Shield that was introduced earlier in Season 8. There have been a few bugs since their introduction, but through numerous updates, in March alone the shields have been slightly tweaked.
Primarily, the major change to Heat Shields that came with the update is that they are now in regular and ranked loot pools once more. They were originally disabled on March 12, but now that they're back they've returned with a few changes as well.
Players can no longer enjoy a fast heal in the heat shields. This passive was given to the item to help players heal up while avoiding the dreaded damage ticks that came from being outside of the zone, but end game scenarios found the shields to be extremely useful. Associate Live Balance Designer, John ‘JayBiebs’ Larson, tweeted out with a request to the community on March 23 after the update was live.
Respawn will continue to monitor how useful the Heat Shields are, and are willing to make whatever changes needed to balance the item. More changes for Season 8 are on the way, and Season 9 leaks may have revealed the next Legend.