Hmm... Usually, when I bring Shale, she tends to do a fairly good amount of dmg. I did a two-hander city elf Berserker/Reaver warrior playthrough and I was able to tank and deal the most dmg out of everyone. I put most of my attribute points into strength and constitution. 2 for strength and 1 for constitution until I maxed the 2-hander ability tree, then 2 into constitution and 1 into willpower so I could grow my stamina pool. Devour really helped when I started losing health. Two-handed sweep really helped when I'd get surrounded. And Indomitable, well... No stuns, knockdowns, or any other physical affects other than getting knocked back if an enemy tried to knock me down. I demolished the archdemon, though I had to use a health poultice every so often, and it was difficult to keep everyone else fighting. But I did, and I killed that motherf@*#er.
When I play as a S&S tank, I put one point each into dexterity, strength, and constitution. When I've maxed out the S&S ability tree, I focus more into constitution. Need that health to keep standing.
I did fight the high dragon without a tank, though. Once. I was playing as my elf mage (Arcane Warrior/Blood Mage) and I brought Morrigan, Wynne, and Leliana with me. All ranged attacks. It took a while, but it worked. I had to keep moving everyone back so the dragon couldn't swipe at anyone, but occasionally, some one would fall and I'd have Wynne revive them. Odd thing is, Wynne and Leliana didn't get hit all that much. Just me and Morrigan. Oh well, I killed it. End of story.