Maybe I was misunderstanding the damage output from Gliscor. Was this pre or post SD?
Cause when I calc it pre SD, I'm seeing non Flight Gem Gliscor doing: 252 Atk Gliscor Acrobatics vs 244 HP/252 Def Gliscor (Impish): 25.57% - 30.11%.
252 Atk Flying Gem Gliscor Acrobatics vs 244 HP/252 Def Gliscor: 38.35% - 45.17%
To make sure the results were the same, I entered a 110 bp Flying-type move instead of Acrobatics and got the same results.
252 +2 Atk Flying Gem Gliscor Acrobatics vs 244 HP/252 Def Gliscor: 76.14% - 89.77%
You HAVE to get a SD in or opposing Gliscor with Ice Fang you. Assuming max Atk / Spe...
0 Atk Gliscor Ice Fang vs 0 HP/0 Def Gliscor: 52.23% - 61.86%
And if you HAVE defense investment, all of the calcs from earlier are doing EVEN less.
Assuming you have 0 Atk investment and have a a defensive spread, a +2 Flight Gem Acrobatics:
0 +2 Atk Flying Gem Gliscor Acrobatics vs 244 HP/252 Def (Impish) Gliscor: 59.66% - 70.17%
0 +2 Atk Gliscor Acrobatics vs 244 HP/252 Def (Impish) Gliscor: 40.06% - 47.16%
With those two attacks and poison heal recovery, that's not a guaranteed 2HKO.
All of these were done
here. They assumed a 244 HP / 252 Def Impish as, honestly, that's the best one =P.