It has been disabled in warzone but not in fiesta. I got 16 kills with the Arclight but only got the gun once.
The reason why the arclight was removed from Warzone was because of an exploit that caused an instant core win. It has nothing to do with arena. You probably just picked up ammo from a dead body without knowing
Halo 5 Arclight Glitch - How it works - YouTube this was happening
Oh, 343i really need to tweak the arclight if that still hasn’t been fixed. Hopefully it gets patched in the November update
That’s a pretty cool bug to be honest. I would love to see what the debug log looks like for it.