@WhoopFighter You didn't mention what mode you were playing, so I had assumed you were talking about pubs due to there being a Rift Relic that achieves what you had described.
If it was in ranked, that's a whole different story, as there's no way to heal outside of legend abilities, (which don't work when you're taking any kind of damage).
In the case of ranked, its either a glitch/exploit or a cheat, (more so a cheat). I've dealt with a few players who's armor I had cracked several times before. These players weren't all that good with their aim, and then they suddenly had perfect aim after cracking their armor a 3rd time.