My ideal party settings consisted of a tank (usually a guy with a 2h weapon such as Sten or Ogrhen of myself an interesting choice here is to use Dog he's not as powerless as you'd think even in the end game) The tanks job was simply to get as much attention on him as possible and to smack the crap out of it, because of how the game mechanics work, enemies target the biggest threat so put a tank in massive armour, give them a massively damaging weapon (the 2handed version of Starfang if you have the warden's keep dlc is perfect for this) and then set them to have Threaten on continuously. Then you have a rogue and a warrior with sword and shield (Zevran is great for less morally good players and if you're playing the evil side of the game perhaps it's not a good idea to use Allistair here just equip Sten and have Alistair train him as a templar if not Leilana and Alistair are the best two for these roles) the rogue is there to open chests, deal with traps and generally you want a great bow on them so they can hang back and not get involved with the melee give them dual wielded weapons if you want them capable in the melee I found most of the daggers from the DLC packs to be brilliant some were better than main game longswords acquired much later in the game! Finally a mage to round the party off now I believe in giving all my mages some healing capabilities even if they don't have the spirit healer mega boost to healing magic. Therefore my personal choice was Morrigan but boy did I have a hard time keeping my good character's relationship values up around her.

Personally I never found Shale much use outside of the Ozramar quests where her abilities and the optional conversation pieces are awesome. Yes Shale is a huge tank of a character but is far slower than Dog and the speed shows in melee, even Sten is quicker and Sten I find to be quite slow by the time Shale gets in to the fight it's all but over if your rogue and melee warriors are quick. Though Shale is epic for just walking around with, especially with Morrigan in the party too they have the funniest conversations.