Over in the Classic Update thread, this caused us to do some investigation:
I believe it is still incorrect to say that warlock pets despawned immediately upon a new summon beginning to be cast. The Debuff “Summoning Disorientation” is supposed to take effect on the existing demon for the duration of the summon cast. If the cast is interrupted or stopped. The original demon is supposed to become unstunned and available for continued use. There are no patch notes showing this was ever added or changed, documented or undocumented. Kaivax please check and see if the debuff “Summoning Disorientation” existed in the old codes. If so, then that is the reason for the discrepancy between what players remember, and what the old code says. The missing piece if you will.
Another issue players reported was that Warlock demon summoning was broken – lots of players said that you shouldn’t lose your current demon until the new one appears. We double-checked and in the original 1.12 WoW, and there, as soon as you started summoning a new demon, your existing demon disappeared. So the demo actually matched how the game played originally. There were a few other reports – such as “rare mobs do way less damage” and “Kobolds at Jangolode Mine run faster than walking speed when running away” – where we were able to confirm that the gameplay was the same in the demo as in the original 1.12 WoW.