Sunday, July 13, 2008

Life Tap and Scaling

Why does Life Tap scale with spell damage?

The simple answer is that spell damage improves your spells, Life Tap is a spell, and thus spell damage should improve Life Tap. However, I think that this logic is flawed, and a scaling Life Tap actually causes some issues with warlocks.

Power Stats like spell damage and attack power work in a linear fashion for individual spells. They follow the general equation Total Damage = Base Damage + Coefficient * Power Stat. Pretty much all classes use this model to determine how the Power Stat affects the damage done by spells or abilities. Even warlock spells use this equation.

However, unique to warlocks, spell damage also changes the ratio of spells being cast. Consider a warlock who just casts Shadow Bolts and Life Taps. At zero spell damage, the warlock can cast 1.3 Shadow Bolts for every Life Tap. For about every 500 extra spell damage, the warlock can cast another Shadow Bolt before needing to Life Tap. 500 spell damage = 2.3 Shadow Bolts. 1000 spell damage = 3.3 Shadow Bolts. 1500 spell damage = 4.3 Shadow Bolts.

What this means that as a warlock accumulates spell damage, the percentage of time she spends on DPS increases. This is in addition to the fact that the individual spell's damage increases as well. So spell damage essentially has a double effect--a non-linear effect--on a warlock's DPS. It increases the damage of Shadow Bolt and, through Life Tap, increases the percentage of time Shadow Bolt is cast.

This shows that warlocks scale in a different manner than the spells of most other classes, and this probably makes them hard to balance accurately for all tiers of endgame.[1]

On the other hand, if Life Tap didn't scale, you can replicate much of the same effect by downranking Shadow Bolt. A downranked Shadow Bolt has a lower cost, meaning it can be cast for a greater percentage of the time, and potentially doing more total damage than the higher ranked spell at some point.

So now I'm not really sure what we can conclude from this exercise, other than once again we show that being able to downrank spells causes problems in WoW. In many ways, costs are most important part of game balance. Being able to change costs without repercussion has caused a lot of balance problems in WoW. One of these days, I hope Blizzard takes this to heart, and removes the ability to cast downranked spells.

[1]DPS warriors also have some of the same double effect, in that AP allows them to hit harder, therefore they generate more rage, which allows them to use specials more often. However, DPS warriors tend to hit the point where they have always have enough rage for their ability cycles relatively early in their progression, so it ends up not mattering as much.


  1. One of the things that I like about Lord of the Rings Online is that it doesn't have ability ranks. Your abilities automatically "level up" as you progress in level, getting minor improvements each level.

    But more on the subject at hand, the solution is likly what was planned a few patches back, and make it a fixed percentage. Honestly, I wasn't really sure what was with all the complaints, because on my 'lock that change would have actually IMPROVED the efficiency of Life Tap. Mind, I don't PvP, which may be the reason, but in my raid gear I tend to have more mana then life. This would change the effect to be more in line with what is normal, in that more Int allows for more casts.

  2. It's the Job of Blizzard to balance the game, and the way of balancing the game should not be to remove all the situation where you cam make decisions.
    Downranking is on way to make the game complexer and more intresting to play.

  3. Down ranked spells tend to have the co-efficients nerfed, such that downranking is penalised.

    Warlocks scaling to their shadow bolts in a way makes sense, since the normal spell rotation for a raiding warlock is:

    10 Shadow Bolt
    20 Goto 10

    Our mana expenditure is very high with very little repetition, life tap tends to result in a high loss of damage potential (17% iirc the numbers overall unless you need to move, in which case its effectively free). Essentially it chews global cooldowns, on the early time of 1.3 shadow bolts per lifetap thats essentially increasing the cast time of a shadow bolt by close to 1.1s (3.6s cast sustained), at 1500 spell damage the cast comes down to a much more reasonable 2.8-2.9s cast (more in line with the actual casting time of the spell), and since we have few other mana regen abilities (fel hunter sacrafices damage, life tap sacrafices dps time, mages get gems - off gcd - and their massive regen) we interlace the mana regen with our casting rather than taking a pot-equivalent (mana gems) or a static full-mana regen spell.

    In essence each tier can be balanced against a lock getting no life taps but altering the speed of the shadow bolt and assuming infinite mana, so a t6 lock with 1500 spell damage will be balanced at 2.8s roughly for their damage / sustained comparison to mages.

  4. The previously planned Life Tap change on the PTRs were terrible for PvP, and that's precisely what it was designed for. The moment that Blizzard realized Warlocks were in-line relative to the other classes, and hence didn't need a nerf, they rescinded the change. Make no mistake about it, PvE and efficiency had little to do with it.

    I don't know any Warlocks doing T5 content or higher content who down-ranks Shadow Bolt, myself included. To me, that's just silly. If efficiency is so important, then Spell Haste rating would be a terrible stat because it increases the amount of mana spent per length of time (e.g. Mana/Minute). Yet we know this isn't true. Downranking for dps casters is never an issue quite honestly.

    I think most people need to be reminded that spell damage is balanced around 100% bonus every 3.5 seconds. Compared to Mages, Warlocks' efficiency is poorer, leading to a shorter chain cast time.

    If Lifetap did not scale with spell damage, this will lead them to receiving a smaller amount of spell damage bonus per duration of fight. Basically, 1000 spell damage would produce more raw damage under 1 minute by a Mage than by a Warlock with non-scaling Life Tap. Quite frankly all Life Tap's scaling does is keep Warlocks in line with other classes who make full use of their power stats.

    If anything, a non-scaling Life Tap would make it more difficult to balance because Warlocks would be the only class not receiving the full benefits of spell damage as a stat per time duration. This will require talent changes to compensate and a lot more headache than it's worth.

  5. The PTR version of Life Tap that was rejected, worked as follows as far as I'm aware:
    Life Tap would drain a percentage of original Hit Points whilst giving a fixed amount of mana back (correct me if I'm wrong).

    So assuming say 3% HP drained, if you had 8000 hitpoints you would lose 240 health and get back X mana, whereas if you had 15000 hitpoints you would lose 450 health for the same X mana.

    rj, I'm not sure how you think that improves your mana efficiency.

  6. The tested version was X% HP lost to recover X% mana, not a fixed mana value. This increases the efficiency of Life Tap as long as you have more mana then health, as well as recovering more in general.

    I think the final tested value was 12% health to recover 12% mana. Right now, I lose roughly 1500 health to recover roughly 1500 mana. But with that change, raid buffed, I would have lost roughly 1800 health to recover roughly 1900 mana. Not only did I recover more mana, which allows for more casts before needing to cast again, but I also recovered more mana then I lost in health.

    Again, though, I don't PvP so I guess the change would have been much less efficient with the ridiculous amount of Stam on PvP gear.