What the hell even happens to Shale? She shows up to help Wynne and then, nothing.
Wasn't she going to go to Tevinter so see about a cure?
Cured Shale for cameo!?
The thing about having a game in the North that I'm excited about, is a whole new cast. As much as I love my DA characters from the 3 games - there better be a BLOODY good reason why they show up in DA4 or I won't be happy. Tevinter cares little about the South, and there aren't many who would happily go for a holiday there. So DAO cast? Only a Sten -> Arishok and possibly Shale would have reason to be up there. DA2? Fenris would have reason. No one else. DAI? Dorian. That's it.
I know it won't be a popular opinion but that's just how I feel. We aren't in the South anymore so the writers shouldn't have to worry about your choices from DAO and DA2. Who cares who rules Fereldan, Orlais or Orzammar. Not relevant in the GREAT IMPERIUM. The Mage/Templar war? Not relevant in Tevinter. Kirkwall? Nope.
For two games the only thing we really heard about Tevinter was 'Slave Trade!' and that was it. Dorian came along in DAI with Calpy and the Venetori to bring a bit more information but still not a great amount. I want that same attitude when we are in Tevinter.
I've played a couple that have switches in Protags.
Assassins Creed series had the switches between past a present with Desmond/Altair/Ezio and Random dude/Edward.
Tales of Xillia has two different leads and you see different parts of the story depending on who you play
Kingdom Hearts Birth By Sleep and Dream Drop Distance both involve switching between multiple protagonists
The Witcher 3 has it a bit with Geralt and Ciri. I suck at playing as Ciri 
Jet Force Gemini! One of my favourites from the N64 had you switching between Dude, his sister and their dog. Damn that game was a pain in the ass. Still love it.
GTAV
I will throw in Borderlands here, because while they may be kinda characterless drones when you play them, they became rounded characters when the four of them show up in Borderlands 2
That bit in FF7 where you play as Cid for a bit.. 
I could be here all night thinking through my games collection. But yeah, I've played a few with multiple protagonists and it is something I have liked.