Guild Wars 2 was designed to support a wide variety of builds AND support large scale cooperative play. While both realities are true and applied to the game, both do not happen at the same time.
Malice, or Condition Damage, is an alternative way for a character to deal in contrast to Power. Abilities based on Power have their own unique variable coefficient, while abilities based on condition damage have variable duration.
The four type of damage dealing conditions (ignoring traited fear) are:
Bleed: Arguably the best condition in terms of damage dealing. It has a low Condition Damage ratio per tick, but usually has very long duration and the most important: It stacks quantitatively.
Burn: Deals a very high burst of damage with high Condition Damage ratio. In compensation, it usually has very short -and only stacks with duration.
Poison: Moderate damage that cuts the regenerating capabilities of the target. Usually lasts for long and stacks with duration.
Confusion: A special condition that damages foes when they attack. Stacks with intensity and is usually applied in moderated quantities (about five stacks) that lasts for a moderate amount of damage.
Both Confusion and Poison are “PvP” conditions that shine at crippling the actions of their targets, while Burn and Bleed are general DPS’ing conditions. While I agree that conditions are fairly balanced for sPvP, WvWvW and solo play, a Malice-based character’s usefulness can be dragged down to close to zero in group play, and it happens because of the way Conditions stack.
Confusion is admittedly accepted as not useful for PvE because it requires the enemy to attack. Your goal is to make the enemy attack as least as you can, by out-ranging, CC’ing, interrupting and chilling. Also, for longer battles, you probably want to reapply your confusion only when the last one has ended/is ending, so you can keep a higher uptime and have a more consistent DPS with it (if you apply 15 stacks of Confusion for four seconds and your and your opponent doesn’t attack once, you dealt zero damage with your condition. But if you keep 5 stacks for twelve seconds, you get a much higher chance of it being triggered. Even works against players, forcing them to either take damage or be controlled for a longer period of time). Poison doesn’t deal enough damage to be your main source of DPS, but it shines at keeping enemies “tagged” (because it lasts long and stacks with duration), making them unable to get out of battle regeneration (you know how frustrating it feels when you end a battle with a Risen Hylek and realize you have 20 seconds of stacked poison duration and no condition removal).
Bleed has the potential do deal greater DPS than Power-based damage. It stacks to 25, which some professions can easily maintain. The downside is that it takes time for it to stack and until then, you don’t deal your maximum DPS, making it very bad at dealing with low health enemies in comparison of the burst damage that comes from Power and Burn.
Burn deals “decent” burst damage, and has a very short duration. Some professions, if dedicated to do so, can apply 100% uptime burn. DPS-wise, it’s worse than bleed at 7 stacks.