If you don't like any of the mages in the lore then you just don't like mages in general. You seem to like dark and edgy type serious classes like DK. Your choices for inspiration then would be limited to Death Knights and Demon Hunters. Warlocks are dark yet goofy. Mages are usually light-hearted and goofy. You proved this point when you said that Kael'thas was a warlock when he wasn't. He was a fire mage. Not once did he do anything related to being a warlock. Pyroblast, summon a phoenix, fire magic, barriers... the only thing questionable was how he managed to resurrect his entire council. Sure, he summoned Kil'jaeden, a big badass demon, but Azshara and Kel'thuzad also either summoned or attempted to summon a big, badass demon. Mages actually have a history of summoning the biggest and most badass demons to date. Sargeras, Archimonde, and Kil'jaeden have all been summoned or almost been summoned to our world by mages.
Anyway, point is every class has their aesthetic and mage is more light-hearted and goofy. If you don't like that then you won't like mages. Khadgar should be a huge inspiration to any mage since he's so cheery despite his many years of hardship. Medivh is a great mage in his own right and he's still out there somewhere. Kinda flew away after Karazhan. There are plenty of cool mages they just usually like to tell jokes. Of course Arthas isn't going to joke around. Death Knights are probably incapable of making a joke anyway. Liches usually do though.