For Warriors sword/shield with the Champion branch is pretty much immortal but something like a 2 handed Reaver does a lot of damage.
The thing with the KE is that it doesn't exactly kill stuff quickly even if it is immortal so if you don't have support spells to keep the rest of your party up you're in for a long boring grind trying to kill a dragon or something.
You can pretty much see my KE's skill bar setup here... http://i.imgur.com/p5S6tqn.jpg
That's my preferred party choice too, champion tanking warrior with a reaver 2 handed warrior, and an extra mage for more dps and extra barriers.
I actually have barrier on my KE even though I make my own doing damage because it's pretty unrealistic to keep it up just with doing damage and having two sets of barriers in the party really helps the warriors stay unharmed. I have a revive too, cause... I'm immortal and Blackwall always stays up, but the other two might die... mostly Dorian... then again, that's probably my fault since he's still in his starter armor since he looks better than the goofy outfit I'd have him in if I gave him better armor... lol
I have Dorian fully specced as a necro with all the necro skills and he has chain lightning, immolate, and barrier. I probably gave him that guardian thing too... pretty sure I have that one as well. It's helpful.
I used to always bring Cassandra and 2 other mages but then after I got Iron Bull and set him up totally as 2 handed it was really fun to play with his earthshaker thing and bull's charge and stuff... and I was surprised how much damage those things do so I kept him around. Then I ended up putting Blackwall in my party because of all these Gray Warden quests... I figured it'd be best to actually have one in my party while doing them... and after I learned about specializations it seems like he's a better tank than Cassandra since he's a champion and she's a templar. As for Dorian, well... he's pretty and he has amusing dialog... and it's kinda interesting having a Tevinter in the party to comment on everything.