I wouldn't really consider him overpowered when half the enemies can just flat out stop time itself, summon demons, and insta kill all your squishy party members within a turn.
The problem with your reasoning is that you expect everyone to have read up on all the dev posts before even playing the game. If you're some dude who just saw PoE and figured "Hey, this looks kinda like Baldur's Gate and I loved that game. Lets give it a try." you'd be pretty surprised by how different some classes were. You shouldn't have to do homework before buying a game.
I can't agree that making fighters that can, you know, fight is a mistake either. It makes no sense that the only class that can master weapons will be outperformed by a half-mad savage or some forest hippie.
you can make korgan effective ignored by demons with a low-level priest spell or scrolls. you can negate most insta-kills with his kit abilities or scrolls. as for the rare time stops, that is why you got your own wizards in a party, but chances are you wouldn't need 'cause your likely super-speed korgan with weapons o' doom has likely killed any but a handful o' bg2 foes in a matter o' seconds. is not much need to argue this further. if you are honest not seeing grandmaster korgan, dual-wielding hammer o' thunderbolts and the axe of yielding as an example o' bg2 op, then poe is clear not the game for you. such munchkiny nonsense is exact the kinda ie bagage the obsidian developers were ridding themselves o' when they built poe. still got got all kinda poe features which is familiar to the ie fan w/o the busted arse korgan example, so claims o' spiritual successor failure is dubious at best.
as for complaining justified ignorance, am unmoved. nobody in their right mind is gonna assume everything 'bout poe would be identical to the ie games, particular as the ie games were so varied. would be impossible to make poe like all the ie games. even so, if you contributed to the kickstarter, then you would get emailed developer updates. read or not is on you. if you were late to the party and simple bought on a whim, then feign ignorance 'cause thac0 were abandoned or dual-classing were missing or the aforementioned insta-kills were removed would be a prime example o' recognizing ye olde warning to the foolish: caveat emptor. again, the reasonable person is gonna assume changes would be made. you not care enough to check what is different is on you. 'course is moot as you is now informed. so congrats. problem solved, eh?
every class in the game is having combat use, so all classes fight. if is simple the naming nomenclature which continues to baffle you, then am amused, but am doubtful there is much help coming your way. get a name-change from fighter to defender seems unlikely at this point, yes? 'course to simple demand poe fighters who can fight ignores reality and the developer response to your complaint. perhaps you did not notice, but poe is a squad-based, tactical combat game with rpg elements. to play poe w/o one or two tanks makes it more difficult for your party to fight effective. heck, we rare do a potd run without a tank and an off-tank. nevertheless, chanters fight. priests fight. ciphers fight. fighters do indeed fight.
also, if you are gonna refuse to read or respond to the actual developer reasons for making the poe fighter, "low-maintenance, reliable, and long-lived even in marathon battles," as 'posed to being able to chunk everything and withstand trebuchet strikes as were the case with 2nd edition fighters, then am not gonna be able to make much headway. we linked. don't wanna read? don't understand? am not seeing how to help you.
am repeating self. until we get word from obsidian, am not seeing a reason to prolong the agony. am actual a bit curious 'bout obsidian plans for a number o' poe classes which mutated with every build... and for the rogue which largely kept its original role and thus became marginalized. 'course is gonna be nothing but conjecture 'til we hear from the developers or get our hands on the beta.
HA! Good Fun!