Wouldn't that be rather boring -- if all three advisors bowed down and supported your decisions no matter what? What if you say you want to go into a situation with guns blazing (so to speak); of course Leliana is very likely to object, and perhaps both she and Cullen will be concerned about the possibility of wasting innocent lives. But ultimately maybe your plan is the best plan in terms of cold, hard victory, so you go for it.
Isn't that scene more interesting that Cullen and Leliana both just bowing their heads and saying, "As you command, Lord Inquisitor" ?
They probably act just like that , though.
Cullen , Leliana , and Scribbles probably won't have any major breaking points like most of our companions.
Maybe they'll moan a bit , but they will do what they are told .
Because I can't imagine putting a player in a situation where you can loose a big part of gameplay because you disagree with one of your generals.
Possible they will try to kill you at the end , when the breach is closed. 