My point is that Zhu Ran, Cheng Pu, Han Dang, Yue Jin, Yu Jin, Deng Ai, Ma Dai and even Pang De accomplished more than Dian Wei, but yet they don't get anywhere near as much recognition as Dian Wei because they weren't playable in Dynasty Warriors.
You mention in your first post Dian Wei's accomplishments which amount to saving Cao Cao from Lu Bu's army twice and saving Cao Cao from Zhang Xiu's sneak attack and being "one of the greatest duelists of all time" despite him only dueling Xu Chu (that I can think of). If you read the bios of some of the men I have listed above, you will see that he did indeed accomplish very very little compared to any of them.
I am not saying that no-one else is over-rated, far from it (I think Ma Chao couldn't be more over-rated...). However, I am saying that Dian Wei is considered to be so much better than generals who did so much more than him for their respective kingdoms and that is over-rating too.
Dian Wei did his job. He was a bodyguard and if he hadn't saved Cao Cao on those three occasions then history could have been very different.
As for Zhang He, I agree that he is over-rated too but he still did a fair bit. He was one of Yuan Shao's best generals before he defected to Wei. He was instrumental in Cao Cao winning Guan Du, helped crush Ma Chao's rebellion, he was part of the force that took Hanzhong and finally was a major part of Jie Ting as you said. So his accomplishments were a little more than Jie Ting...but not a lot more