Imo, yes to some more gimmicks. Sure, the main eventers right now have different personalities, but it doesn't add nearly as much on camera as it does on paper.
Jericho: I'm an asshole because you praise HBK for doing mean things.
JBL: I'm an asshole because I made it big in the stock market and therefore idolize Gordon Gecko. Greed is good.
RKO: I'm an asshole because Evolution betrayed me and now I hate everything.
Batista: I'm not an asshole currently, but I want the title. If I WAS an asshole right now, it would be because I want the title. The only reason I'm not an asshole now is because the guy who has the title is already an asshole and if there were two assholes that would rip apart the fabric of reality just like if you divided by zero.
HBK: I do assholey things, but you love me anyway.
Kendrick: I'm an asshole because I'm always been one. London is a douche.
Edge: I'm an asshole.
Notice the pattern? They're all just angry guys. Half the time I feel like you could swap _______ for _______ and you wouldn't have to change the dialogue. What we need is a greater emphasis on those personalities. Orton apparently snapped, and is now psychotic, so play to that even more. His song talks about hearing voices that make him want to hurt people, so do that! Have some promos of him talking to himself, amp up the anger in his conversations, etc etc. Make him unique. Like someone said above, why isn't Punk's "straight edge" thing being emphasized more? The unique gimmick is right there inked on his fists, WRITTEN ON HIS BODY, and STILL somehow the writers miss it. And why exactly isn't Jericho cracking jokes in his promos? It works just as well as a heel and it'd give him a hell of a lot more personality than he has now.
Guys like Kofi, MVP, Santino, Kozlov, etc, add much needed depth and unique personalities to the show. A show where it's just angry guys who talk generic trash gets very old very quickly. Gimmicks don't have to mean Papa Shango (though Roxxi pulled that off and is now over, hint hint), they just have to mean personalities unique enough for the scripts to not be interchangeable. And yes, there is room for "normal" people. But right now, we're running on empty in terms of memorable personalities.
And as for "out there" gimmicks, don't try to tell me a well written Kane promo doesn't creep you out. Monster characters are great for putting over the midcard, and if they're done right they themselves can be main eventing as faces. Look at Undertaker.