SoD classic, if a warrior ques heroic strike, the spell que window breaks. This was an issue in WotLK and I recall it being fixed around half way through the expansion.
To recreate it, you test a spell (like sunder armor) then when the GCD is about .3 seconds from being ready, tap it once again and it will que it and then cast it the moment that GCD is ready. However, if a heroic strike is qued when you tap it, it won’t que. Meaning if you have a ping of 100, your GCD is actually 1.6 seconds instead of 1.5 anytime heroic strike is qued. If you ping is 300, your GCD is 1.8 seconds. You have to keep mashing the key well beyond the spell being ready to actually cast it, whereas with the que window functioning you dont have to do this.
Over a boss fight, this can push multiple spell casts off your rotation over the course of the fight. I.e. if your ping is .2 seconds, and you cast 100 spells, you can see about 20 seconds of casts get lost if you had heroic strikes being qued that entire time.
The bug was fixed in WotLK so its possible to fix it. Somehow in the different versions of the different clients this was reintroduced into classic wow, or the era client never had it changed as the classic client is a different launch option.