I haven’t really heard any discussion about spell queing in classic even though as far as i can workout it was definitely not added till later expansion. (believe the option to change the customlag tollerance value was added in cata, but can’t recall if it existed with a straight tick box before that)
The reason i think it’s worth discussing is it provides a somewhat significant dps boost, especially to players with higher latency. As it completely removes any gap between 1 cast ending and the next cast starting that would of happened in vanilla. It also significantly reduces the need to spam abilities just as they come off cooldown.
While i think spell queuing is a great feature in retail, i personally feel there is definitely more of a concern in classic that the game is already pretty easy relative to vanilla. Do we really need yet another buff?
Also i wouldn’t be surprised if it subtlety effects game balance, as i imagine certain classes would lose a lot more time.
obviously the big argument against it, is it in effect creates a world where people with high latency internet do less dps, which just kind of sucks