Vanilla classic had a fair bit of bugs, but vast majority of them were non intrusive enough to just ignore em, TBC had bit more (many never got fixed) but WotLK seems so bug-ridden It makes me not wanna play it.
Seriously, even servers "we can't talk about" make Blizz version look like its made by amatours that just didn't give much fk about it.
Aaan I am not talking about some very technical stuff like which effect should proc what at what rate etc.
Equipement menager is straight up broken and doesn't work at all as it is supposed to work, "ignore slot" doesn't work, when you delete set you get lua errors and are unable to get rid of now broken saved set XD
Hunter pets spawn after dismount with around quarter hp, despite being full hp before mounting.
You can't cast buff spells with ranks on lowbies if given spell is cast via a macro or clicked on it in spellbook, only when dragged out of spellbook and dragged onto action bar.
You can't take standard pet controls (like attack, follow defensive stance etc) off pet action bars, you deffinitely could in WotLK.
Whole thing gives vibes more of stiched together frankenstain (or patchwork) rather than either a "museum" of WoW nor modern, improved game. It has worst out of both worlds...