its similar to when you get Head of the Dragonslayer debuff, it doesn’t go out instantly and takes quite a while to show as a buff, of course this is server lag on top of just the default 400ms spell window, its the only thing I can think of that can explain it “working as intended” yet still feels completely broken.
I have noticed if i queue a frostbolt at an enemy and instantly frost nova the nova is instant and hits the target first then the frostbolt crits them instantly breaking the nova, similar things might be happening with gouge/blind/seduce/sheep, the only thing I can suggest for yourself is to have a /stopattack added to your gouge attack, so you don’t instantly break your own gouge.
something like this:
#showtooltip gouge
/cast gouge
/stopattack
Now i know gouge is meant to stop your auto attack so this shouldn’t be needed but it forces the game to prevent your attacks from landing in the same spell pool/batch.
when server lag is high the batch window increases dramatically, say you’re dueling outside stormwind when the Dragonslayer buff goes out, you get a good extra second or so of response to all spells/abilities making them do strange things.
have a read through this blue post if you’d like to understand it a little better they explain it fairly well. Spell Batching in Classic