Casting Speed vs. Spell damage

As of any additive stats in game, there's diminishing returns as you stack them higher. Which applies to %increased spell damage & % increased cast speed. I spent about half hour trying to get a graph of spell damage vs cast speed for flame totem to see what's the optimum value for both with no luck.

If there's already a program/spreadsheet to compare spell damage/cast speed out there, please link it here. Or if someone can make an excel to compare the two, i would be grateful.

Lets take Level 20 flame totem for example
cast time: 0.2 seconds = 5 casts per second right?
damage: 61-92, i was measuring with 61 to make it easier to calculate.

For area maximization with two scalars multiplied (dps = damage * speed), you always want a Square of Happiness. If you get more of one than the other, you produce a Rectangle of Inefficiency.

ex:
2 dps = 2 dam * spe, you double your dps and it takes 100% increased damage
2 dps = dam * 2 spe, you double your dps and it takes 100% increased cspd
2 dps = 2**0.5 dam * 2**0.5 spe, you double your dps and it takes 41% increased damage and spd (82% "increased" in total)

Given that you can only affect multiplicative increases to the base stats of the spell, the actual base stats don't really matter at all and it's only the increases/mores that you are interested in.

However, this assumes that it's free to get an infinite amount of either, and the only thing you care about is the ratio. This isn't the case in PoE. There's a fixed amount of increased/more damage and increased/more cast speed available which depends heavily on your gear and other things you need on your tree.

Your best bet is to draw up a tree that takes only defenses/keystones, and leave yourself a budget to solve for "damage". With those outside considerations out of the way, it's a much cleaner problem to solve.

Another consideration is that people usually avoid cast speed because it directly scales their mana/second requirements. Using a totem, you're free to get as much cast speed as you please since it doesn't increase your mana costs.

---

As an aside, diminishing returns isn't the correct word, and it often gets used incorrectly. "Diminishing Returns" implies that one of the scalars stops scaling linearly as you get more of it. If, after 100 cast speed, it took 2 more cast speed to get to 101 cast speed, that would be diminishing returns.

The only stat in the game that has actual diminishing returns is IIR, and the diminishing function is secret info that only GGG knows.

Thx! excellent answer, i did get a linear graph for both cast speed & spell damage with increments of 10-20-30% which i thought was probably wrong. but your explanation confirms it!

spell damage & cast speed scale in exactly same way & your point about mana issue of self cast vs. totems makes me want to get more cast speed as i have huge pool of spell damage & only 10.5 casts per second on flame totem, still have 3500~ tooltip dps at lvl 71 with pretty bad gear.

now i wonder how much cast speed is possible with gear & tree, gonna spend some time looking into that!

Although its true that cast speed should be grown equally to damage for optimum dps, its also true that the nodes are not equal. For 3-4% cast speed you can get 8-12% damage. Its also true that there is a faster casting support gem and no increased spell damage gem. For balancing resource investment, you should take this into account.

Lately to considering what my character builds are capable of lategame dps I've been using PoE Builder. I'm not entirely sure of its accuracy but the numbers it gives me usually sound reasonable.

As pneuma stated, increased rate causes your costs to go up. Faster casting = more mana/life required every second.

Increased damage makes each cast more effective, and this means you have more reflect to deal with. This is a problem that Discharge and CoC builds had until they found out how to get around it.

In short, you want to deal enough damage that reflect isn't a problem and at a fast enough rate that you can sustain it. Any more and you begin to lose efficiency. More is not always better.

Just to make sure you know.

Now consider crit % and crit multiplier and my head just explode....

"

Pion33r wrote:

damage: 61-92, i was measuring with 61 to make it easier to calculate.

Use 76,5 instead for your calculations if you want to get something realistic out of it.
You know.. the average of that damage range =)

while the 1:1 balance is true for flame totem since it has no possible "more" multipliers, its not true in general

for example is you are using conc effect fireball spell damage will be more effective than cast speed due to the multiplier on conc effect. Conversely if you are using the new spell echo and nothing else, cast speed will be more effective.

and thats ignoring mana cost, crits and elemental effects which adds a lot more factors ...

So, 9% cast speed or 30% spell damage for totem? :)

"

So, 9% cast speed or 30% spell damage for totem? :)

Typically that depends on how much of each you already have...