Often, if a talent (or glyph) says something like “increases the damage of x by” or “decreases the cost of x by” it seems like a great talent automatically. Especially if x is a skill you use often. Sometimes this method of analyzing proves correct, such as in the case of Glyph of Frost Strike, which is incrediblawesome. Other times, looking at talents and glyphs this way can lead to bad decisions. Some talents are more subtle in the ways that they increase your DPS and so it can seem unintuitive to take them. For an example, I’ll compare two talents, Morbidity and Dirge, for an Unholy Death Knight.
Morbidity isn’t all you crack it up to be
A 15% increase in damage to Death Coil, a spell that Unholy uses a lot, seems great. The yellow numbers you see will get bigger, and so hooray, more damage being done! That said, if you consider that on an average fight, Death Coil usually averages ~10% of your total damage, 15% of that doesn’t seem so exciting anymore. 3 talent points spent here will give you a 1.5% DPS increase (I’m only considering the Death Coil part of the talent because as DPS, you rarely need to AoE so often that the cooldown on DnD becomes limiting).
A general rule of thumb in taking talents for a DPS class is that a good talent point is worth roughly 1% DPS per point spent. Not all talents reach this standard, but at ~.5% per talent point, Morbidity is lower on the totem pole than some others (even Necrosis, despite its nerfs). Note that certain fights will skew the amount of damage a certain skill can do. Take Hodir, for example. This fight may bring Death Coil up from its usual ~10% of damage due to the Singed debuff that makes Hodir take more spell damage. With that in mind, let’s take a look at a talent that’s more consistently awesome.
Dirge, on the other hand…
See this post on EJ by Methods, one of the more mathy-skilled posters. Basically, what he says is that in a typical Unholy rotation, Dirge will net you 1.19 RP per second. Not only does this lead to more Death Coils than you’d otherwise get (1 every 40 seconds), you also have more RP available in general. This will make it easier to activate AMS and IBF, both extremely useful in almost every raid encounter. I believe that Dirge is more of a must-have talent than Morbidity, although its benefits aren’t immediately obvious.
Similar reasoning is applied when Frost DKs using the HB glyph choose to spec into Epidemic rather than fill out Dark Conviction. On the surface, 4% crit seems pretty sweet. It’s important to note that 1% crit does not mean a 1% increase in DPS. It’s closer to around a .5-.6% increase. Running a rotation with the HB glyph is all about getting Rime to proc and refreshing Frost Fever essentially for free. Epidemic, while it doesn’t always help you do more damage like Dark Conviction does, gives you more time to wait for a Rime proc, the using of which increases your DPS.
Next time you see a talent that looks exciting, think about what benefits it offers and compare those to other available talents. Especially when some talents don’t obviously increase your damage output, like Improved Unholy Presence (IUP). This is a hotly debated talent because it’s effect on DPS is hard to quantify. Sometimes, moving faster will get you back into melee range quicker, letting you start hitting the boss again, which is a DPS increase. The most important aspect of IUP is that it will help you survive, whether you’re moving out of fire or onto a pile of snow, you’ll get there faster and take less damage overall. Personal preference comes into play here. If you feel like you don’t need much help running out of hazards, don’t bother with it. If you frequently die on the edge of something that’s hurting you, give it a try.
In my opinion, the ability to choose between talents based on personal preference is what makes the Death Knight a great class when compared to, say, a Retribution Paladin. Ret Paladins basically take every DPS-related/non-PvP talent available to them, so there isn’t a lot of wiggle room or choice involved. I enjoy playing with a talent calculator almost as much as actually playing!