What’s wrong with Bard in your opinion? Technically Kodo raiders in Warcraft 3 can be seen as “bards” and there are more or less NPCs playing instruments. It could be a nice support casting class and I don’t see a problem with another cloth wearing class. I’d love to see another bow/gun wearing class but maybe without pet this time. Maybe do like with Warlocks and “extract” Marksman from Hunter class and make another ranged one that doesn’t have pet.
4th shaman spec would also feel natural since Ele is fire themed, Enha is air themed and Resto is water themed (baded on Ascendance forms and class mount from Legion). The only one that is missing Earth Element themed spec. Guardian Shaman feels right. It can be 2h shaman with recycled Rockbitter, Boulder Smash, Stoneskin and Stoneclaw Totems.
Other than this can be Necromancer class. It’s quite iconic to Warcraft 3. It can have 3 specs like DK Blood, Unholy and Frost. Where Blood can be implementation of Blood Mages (San’layn) and a healer, Frost - a lich themed Shadow/Frost caster that would be less mobile than Mage and Unholy - summoner using two skeletons - one meele and one ranged working similarly to the current Necrolords Priest legendary - more damage you deal when your skeleton mage is summoned - more damage you deal