The ideal party depends on a number of factors: nature of the encount er, size of the enemy group, play style, and more. Here are four configurations that serve in many all-purpose situations.
Balanced
Warrior (Tank) Mage (Healing) Rogue (Scouting, DPS) Mage or Warrior (DPS).
Blitzkrieg
Warrior (Tank) Warrior (Off-Tank) Mage (Healing) Rogue (DPS).
Control
Warrior (Tank), Mage (Healing), Rogue (DPS), Mage (Crowd Control).
Unbalanced
Warrior (Tank) Warrior (DPS, Off-Tank) Warrior (Ranged) Mage (Healer).
A balanced party contains a warrior as the tank, mage as the healer, rogue as the scout, and mage or warrior as support. This configuration spreads the talents around and prepares the group for any challenge. Some abilities overlap, which helps in cases where a companion may be overwhelmed at a critical time, or has already fallen in battle.
The "blitzkrieg" configuration emphasizes speed and damage over healing or defense. You carry at least two tanks on the team, a combat-oriented rogue for more damage and some light healing with a mage who also has offensive spells at his fingertips. This type of party plans to rip through one enemy group before a second can engage them; they don't have the defenses for prolonged fighting, so it's got to be swift or not at all.
A party that concentrates on control stands behind healing and crowd control abilities. You still need a warrior tank, and you need a dedicated healer, which falls to a spirit healer mage. The rogue lays down a lot of DPS, but must be flexible enough to off-tank once in a while or throw out some crowd control (such as a bard's Captivating Song). A second mage brings offense to the table, of course, but also spells like Grease and Crushing Prison that can slow or stop extra enemies from engaging. This particular party may enter long fights, battling for continued periods of time with solid healing and abilities that dictate when enemies confront them.
An unbalanced party may not share abilities optimally, but it can be a lot of fun nevertheless. The idea is to overbalance with a single class or strategy and pursue it to the max. You can generally get away with any combination, so long as you have a mage healer in the mix (parties without a healer won't do well unless you have unlimited health poultices at your disposal, and that gets very expensive). In this example, we have three warriors, fully armed and armored, who can charge into melee if there aren't any ranged threats, or engage and leave one warrior back to shoot down targets at range and act as bodyguard for the healer in the rear. A three-warrior group dishes out tremendous damage and has serious defensive resilience, even if it lacks the finesse of a rogue's touch or the all-out AoE firepower of a DPS mage.
We all know that the perfect combination of party members doesn't automatically mean success. You have to apply your skills and react quickly to the challenges that will inevitably assault you during quests. Smart parties will identify which mobs they can handle and which they can't, and as long as you dodge or control the additional enemies that wander in your direction, your team will thrive in style.
Let's take a look at a sample fight with a tank (warrior), healer (mage) and two DPSers (rogue, mage DPS). You've cleared a path to the boss, and now it's time to take the ugly mug down. Before you launch the first attack, make sure all characters have the proper gear, usable items, and talents ready to go.
As the tank readies his weapon, the healer throws a precautionary Regeneration on him, which serves as a little extra health at the start of the battle and absorbs a few shots. Only then does the tank charge in and hit the boss with Taunt, or whack him a few times to activate Threaten, to draw the monster's attention for the first few seconds.
The mage DPSer holds his ground. He will out-damage the tank if he rains down destruction alongside the tank. The rogue circles behind the boss to get into backstab position (but not close enough for the boss to strike him with AoE attacks). The tank rolls into his offensive routine, smacking the boss with his best chain of attacks.
After three or four attacks from the tank, it's the DPSers' turn. The mage begins his offensive rotation of spells, while the rogue darts in and backstabs the boss. The rogue continues the assault until the boss turns its attacks on him.
If this were a full group instead of a single enemy, the roles would stay the same, except the party would generally concentrate damage on the weakest foe to reduce the numbers quicker. If there was a dangerous foe on the battlefield—for example, a genlock emissary casting spells—charge it with your tank and DPSer, unless the ranged DPSers can take it out.
With the tank dealing steady damage, the mage and rogue supporting as DPSers, and the healer concentrating heals and regenerations on the tank to keep him healthy, the party will take down the boss after a short fight. If the boss pulls out AoE attacks, or brings in enemy allies, the healer should cast Group Heal when possible to keep everyone's health up.
It's important for every member of the group to keep the self buffs, group buffs, and debuffs up at all times! If it's about to drop, refresh it and continue your DPS on the boss. Group buffs/debuffs can have a dramatic effect over the course of a battle. Remember: Damage-reducing and damage-mitigating buffs can translate directly into heals and mana saved for your healer over the course of a fight.
In the end, a team playing the right roles will conquer dozens of enemies.