Whether Orton comes back as a heel or a face won't be a major factor, in my view, because the guy's going to be massively over no matter what. Personally, I'd rather see him as a heel. Everything about Orton's character, from his mannerisms to his character's personality and to what we even know about the guy in real life all practically scream heel character. He's much better as a heel but he'll get over no matter what. When a guy can cause 10,000 people to pop just by turning his head and glaring as if he'd done a moonsault off the top of a cage in a HIAC match, the rest is academic.
As for Dolph Ziggler, I think WWE should keep him as a heel for the time being. If WWE is able to secure a deal with Ric Flair and they go through with the idea of Flair being Ziggler's manager, which is said to be a popular idea among WWE officials, then Ziggler most definitely needs to be kept heel. I think we've gotten some glimpses of what Ziggler brings as a character but WWE really hasn't pulled the trigger on him yet. Like most other people right now, I want to see what Ziggler has without Vickie. He's improved a LOT in his promos and he's actually developed an on-screen character that it's easy for fans to rally against, but he's long since gone as far as he can with Vickie. I think that Ziggler could really step up his game with someone like Flair managing him.