My party was mostly Fenris, Isabela, and Anders, and I played a pro-mage, anti-slavery sarcastic Hawke who didn't take things seriously but really loved getting in people's business. So my approval was all over the place and it was really difficult to get them maxed out (in either direction) without preplanning. 
This made me laugh 
I understand the issue you had in your story, though my experience was really different.
In my last DA2 game-play I was a mage, and my companions were usually Anders, Isabella and Aveline (though I brought Varric and Fenris every now and then, for a change). It wasn't so hard in this case to be friend with both Aveline and Isabella, even though a few decisions provided opposite reactions from them. It also wasn't hard to be rival with Merrill this time, because though I supported mages, I disapproved her use of blood magic. The thing is, even though your general decisions can create reactions you don't want for your rivalry/friendship goal, the personal dialogs with each character (and the lines you say when giving a gift, which is not an automated approval bonus anymore), and especially their companion missions, usually have a much higher bonus in the direction you want. So I didn't find it so hard to be rival or friend with whoever I wanted, while maintaining my character's decisions consistent.
On the contrary, in DA:O I couldn't make my character's decisions consistent with being friend with everyone...
[spoiler ALERT: ABOUT THE FINAL PART OF DA:O]
...When I decided to kick Alistair and keep Loghain, my decision really didn't make sense for a character that had been so nice to Alistair during the previous months. The thing is, as a character I wanted to hate him, but as a player I wanted a good tank with a good combat bonus. I understand the rivalry system in DA2 wasn't perfect and penalized neutral decisions (just like every dual morality/approval system in video games does, the only solution to this is a non-dual system, which I guess would be much harder to develop) but in my personal experience it didn't cause such flagrant contradictions as the DA:O system.
But I might have a different opinion if my DA:O character had been a tank warrior instead of a dual-weapon rogue 