Raid bosses have no level indicator other than the 30 on selecting the difficulty of a raid. To assume Atheon is 31 is only speculation and there's no real facts to back up that statement. A lv 30 with a icebreaker and weapons of light deals 18k damage. A lv 31 with a icebreaker and weapons of light also deals the same amount of damage because bungie made raids scale down in damage to what the enemies levels are so players don't gain an advantage by higher weapon damage and higher light levels. If by that theory, Crota would be 34 but that would make Crota's end hard mode nearly impossible to accomplish. When we're lvl 33, Crota's hard mode will take only take 2 swords to kill like it does in normal mode because all the enemies are 32 and a lv 32 sword wielder can kill Crota with 2 swords. Lv 31's can beat crota on normal but that requires 3 swords just like it does on hard mode for a lvl 32 to beat crota.