Black Mage Dps Rotation Guide! in 90 Seconds!

[HoroBoro]

Scathe is 120 potency. With 20% chance for double damage (crit is not double), that makes it 120+.2*120 = 142 potency.

Blizzard 1 has 150 potency making Scathe the lowest potency spell in the THM class that does damage.

Yes - you have mobility with it and you can kite with it, but it's not something you want to cast if it can be helped.

[AsheliaDalmasca]

Scathe is 120 potency. With 20% chance for double damage (crit is not double), that makes it 120+.2*120 = 142 potency.

Blizzard 1 has 150 potency making Scathe the lowest potency spell in the THM class that does damage.

Yes - you have mobility with it and you can kite with it, but it's not something you want to cast if it can be helped.

Sorry but your math is a bit off there, a 20% chance for a double damage proc does not calculate into potency. The 20% chance is a proc rate not a damage increase.

[Mishaela]

Sorry but your math is a bit off there, a 20% chance for a double damage proc does not calculate into potency. The 20% chance is a proc rate not a damage increase.

What are you even talking about? The skill reads "20% chance potency will double." A 20% proc for double potency makes the spell have an effective base potency per cast over time of 144. In the same way, Fire's effective base potency per cast over time is 150 + .4*220 = 238 because of Firestarter procs (however, one mustn't forget to consider the extra GCDs consumed by Firestarter procs, which really gives Fire an effective base potency per GCD of 170).

In case anyone is not following the math, consider this:
On an average day, you cast Scathe 10 times. Since it's an average day, 2 of those casts will double their potency. That means you did 12 casts worth of potency (12 * 120) with 10 casts for an average potency per cast of 144.

Assuming your spell speed puts you at 2.4s cast/GCD, with 10 casts you're doing ((12*120) / (2.4s*10)) = 60 potency per second with Scathe.

On an average day, you cast Fire 10 times. Since it's an average day, 4 of those casts will proc Firestarter. Using those procs will give you an additional 880 potency on top of the 1500 from the 10 Fire spells. However, you actually had to use 4 more GCDs to cast the free Fire IIIs. That means you did 2380 potency with 14 GCD casts, which is 2380 / 14 = 170.

Assuming your spell speed puts you at 2.4s cast/GCD, with these 14 casts you're doing ((10*150 + 4*220) / (2.4s*14)) = 70.83 potency per second with Fire+Firestarter however this doesn't even take Astral Fire into account which is a huge boost in damage (AFIII is almost double damage IIRC?) that Scathe doesn't get.

[edit]
Obviously, your MP can't sustain casting 10 Fires in a row, so in reality you'd need to consider the dip in damage you'll get while spending a few seconds in UI3 to get your MP back, but even then, when compared to Scathe, this dip is far, far overshadowed by the damage bonus that AF3 gives to your Fire spells, plus those few "come up for air" seconds in UI3 are also your window to reapply your DoT whose damage we're not considering here, either.
[/edit]

tl;dr Scathe certainly has its uses (like when running around dodging titan's attacks or tagging mobs in FATEs or at the last boss of CM, for example) but spamming it when you don't have to move is bad DPS.