This is DAO fault, unlike DAI where you have advisors and others people who work to solve the problem on their own, in DAO and DAA the HoF do the 99% of the Job Alone, it's even possible if you are good with tactics to win in Denerim without calling the army (with 3 rouges,traps and stealth ability it was super easy).
The Warden from DAO (who can acess to an incredible number of Talents or spell unlike the Inquisitor) can risk to die only with the soul of the Archdemon, otherwise he/she is out of the league of every DA characters (Mythal,Urthemiel;the Mother,The Architect,thousands of darkspawn,Ogre,Dragons,ecc...) all of them defeated by the HoF despite their legends.
SO this is pretty much DAO fault to have portrayed the Warden (aside from that forced debacle on the tower of Ishal) like a "21st century killing machine" rather than a simple mortal.
I can't disagree with you there. The Hero is larger than life, especially by the end of Witch Hunt. You're also right about the Hero having more talents. Just look at the specializations. You can get two in Origins, another in Awakening, and another in the DLCs (glitch, not official).
There is the option of lowering the Hero's "power level" since ten years have passed, but the Power of Blood negates this with Heroes who drank the concoction.
I wouldn't necessarily put the Hero out of the reach of entities like Mythal. Power doesn't always equate to victory. If Mythal knows spells that the Hero can't counter, or if Solas has plans that the Hero can't see through, then those characters will pose a challenge even to the strongest Hero.
Not only Ishal, but the Silverite Mines as well. Both were pretty BS. I would have had Ishal end with a bright flash of light that knocks everyone in the room out, including the darkspawn. That would imply that Flemeth is the one who did it just so she could capture and use you. The nerf in the Silverite Mines was just unacceptable. I could tell the platform was a trap as soon as I saw it. There's no way my Hero would have fallen for it. And to have the Architect in a position where he could have done anything he wanted to you is beyond insulting. He even wrote about how he thought it might be best if he just killed you right there. The only reason he doesn't is because he needs you to kill the Mother for him. They could have easily replaced this with a scenario where you have to rescue some of the captured Wardens from Vigil's Keep. As for the lost items and duplicates you fight, they could have explained that away using magic or something. A combination of teleport magic to take the gear combined with blood magic and necromancy for the imposters.
But, the next game could tone down the Hero somewhat to be balanced, or simply increase the skills of the other characters to be somewhat on par with the Hero.