We have legion to thank for fixing the burning crusades screw ups, the burning crusade lore on the other hand was a mess of hamfisted villiany. At the end of the frozen throne illidan and kaelthas were both anti heroes, heck its even a stretch to call kaelthas an anti hero when he didnt fight anyone without provocation, he was pretty much a straight up good guy who looked into demonic magic to sate his races addiction, which we know if not sated causes them to devolve into wretched.
Last we saw of illidan in the frozen throne, he liberated outland, saved the draenie (or broken) and launched a failed final assault on arthas. yeah he had his edgy moments but he was clearly doing things for the right reasons, nothing the burning crusade gave him