Whatever website you were looking at is bogus. I could rant on this for a while so here's the short version. No 3 comps are gonna open all quest lines, talking to them will open some tho. Scoure DA:I Wiki if u really want to know who best to bring for what battle...but then u get into how they are speced. Example, Blackwall sword and board? Blackwall 2H? And u get enough points to spec them in at least 2 full trees...so wich ones? who knows. Sorry to say but your question, imho, is un answerable. Im a elven archer... I roll with Blackwall-Sword and Board/champion, seems to fit his Focus ability well. Cassandra 2H, Templar/2H, and Vivienne, Full Frost, Knight Enchanter, and Spirit for Barrier. Her Focus ability, Resurgence, is a must, Fully revives all party members at full Health/Mana/Stamina. Useful for the Higher lvl Dragon fights. Opinions will vary...but I roll over everything with this group. Potions, Grenades, and Tonics are your friend....use them. Hope this helps a bit. The only way you are gonna experience ALL possibilities is more than 1 play thru.
