I'm not really a fan of the combat in this game, so I've been playing through on casual. I do have the ultimate edition though, and I want all the trophies, so I'll have to do those DLC bosses on nightmare. Now I'm thinking I'm not going to do the DLC on this playthrough (warrior), as I really didn't pay much attention to my build. But is there a consensus as to what the "best" class is for these challenging battles? --- How appropriate, you fight like a cow!
Two-handed Warrior is probably the easiest, as you basically just run in, draw aggro from everything with skills, then beat on everything till they die, while a Mage heals you. If you are also a Templar and use the right armors, you can also make yourself extremely resistant to magic attacks.
Mages and melee Rogues have a lot of tactical positioning to work out (particularly on higher difficulties for the Mages), and all other types of Warrior are outclassed by Two-handing.Archer rogues are pretty easy to play, but also probably contribute the least to the party (other than maybe archer and dual-wield warriors, which I've not really played with).
As far as optimal building and Nightmare difficulty, there is a consumable item in Awakening that lets you completely re-allocate all types of points on a character, and this item is purchasable en masse at a shop.
To add to Rajamic post. 2H warriors get immunity to stun and knowdown(this alone makes them one of the best choices).
They get 2 auto critical skills(although Mighty Blow is way better the Critical Strike) and a cheap low costing knockdown.
They also get a 50% chance to stun on all critical hits, can also debuff Attack and Armour ratings and to top it all off they get the great Two-Handed Sweep talent to help with crowd control.
About their only drawback is their somewhat slow attack speed but you can fix that with a mage's Haste spell or a swift salve if you ever want to attack faster. --- PSN Drmoogle. RPG fans should check out Ni no Kuni: Wrath of the White Witch