If you follow my blog you may remember I spent many agonising months grinding heroic slave pens, waiting for the final boss to drop his trinket, quagmirran's eye. If badges had not been an issue, I would simply have bought the icon of the silver crescent instead and been happy at that. The icon beats the eye in all ways. But I was saving my badges for a weapon. The irony is not lost on me that I didn't buy the weapon but instead only this week bought the icon after all. But I'm not going to dwell on that.
So now I have both the icon and the eye, as well as a third trinket, darkmoon card: crusade. But only two trinket slots. Choices choices.
The icon goes in slot one. It provides a flat spell damage increase of 43, plus a boost of 155 for 20 seconds every two minutes. That's dreamy. My dilemma is which of the eye and the card to pick for slot two. Here's what they do:
Quagmirran's eye: increases damage and healing done by magical spells and effects by up to 37; harmful spells have a chance to increase spell haste rating by 320 for 6 secs.
Darkmoon card: crusade: Equip: harmful spells landing on an opponent gives you 8 spell damage for 10 seconds, stacking up to 10 times.
Quagmirran's eye provides a flat increase to spell damage plus a random spell haste bonus. The haste bonus, I can tell you from experience, will reduce casting times and the global cooldown by about a sixth. This proc essentially enables you to do more damage in the same space of time, so in that respect the trinket is the equivalent of more than just the 37 spell damage it provides on equip. But I don't know how to calculate its true worth so for the basis of this comparison I'm going to ignore the haste proc.
The darkmoon card increases your spell damage by 8 every time an offensive spell successfully lands. (It also works for melee but we won't go there). It stacks up to 10 times, so at maximum increases spell damage by 80. This buff lasts 10 seconds, but is renewed every time another offensive spell lands so as long as you are casting it remains active. Helpfully, non-damaging harmful spells, such as vampiric embrace, proc the effect; resists, player buffs and heals do not. Also, it's useful to know that this buff carries through regardless of your target — you could dot up 10 different mobs or focus-fire on one, the buff will still stack nicely.
The eye then has a head start. It will take you five successful casts to stack the card buff to a point where it provides a greater spell damage increase than the eye. This will take you at least 7.5 seconds — actually nine, when you consider you won't get the benefit of the buff till your following spell cast. During these opening seconds with the card, your spell damage is inferior to the eye, but it will get better as you continue casting. I'm no theorycrafter, but if it took 7.5 seconds to bring you on par with the eye, I assume it will take an equal time of constant casting to break even in damage done. In other words, in a dps race between the eye and the card, it will take the card 15 seconds to pull alongside, and then ahead, of the eye.
In practice, it won't work quite this neatly. Your spell rotations will vary, lag will affect cast times, and the nature of the encounter may necessitate periods of moving or doing other things, not to mention the fact that we're working using 1.5 second cast times and mind flays are 3. In reality, it would take a fair bit longer than 15 seconds for the trinkets to draw level. But remember that your dots get the benefit of your spell damage at the time of casting, not as they tick along, so even if the card buff is not fully stacked, it might still be the better option for dps.
My general rule of thumb is this: If a fight is long enough for you to apply a second vampiric touch, the card is probably the better trinket. On boss fights, it almost certainly is, but this is probably true equally on fights with short-lived trash mobs — providing you are able to move from one target to the next without dropping the buff.
My conclusion: darkmoon card: crusade is the best trinket for raiding and instances. You see? Bleeedin' obvious. Ho hum.
But I'm not getting rid of quagmirran's eye just yet. It's still the better trinket for grinding. Nothing takes 15 seconds to kill and I never cast 10 spells per mob. In fact, I rarely cast more than four or five before switching to a wand. By the time I arrive at the next mob, chances are the card buff has dropped off. It's rather annoying to know I now have yet more things to switch between when grinding or grouping. At this rate, I may even think about getting a costume addon. But at least I know I've made the right choice in raiding trinkets.