Demonology is a filler-and-upkeep rotation. You keep a curse, a Bane, Corruption and Immolate on the boss, cast Shadow Bolt in every gap, and Life Tap when your mana runs out. Your Succubus fights on its own.

Before the pull

The setup takes about half a minute, and our simulator starts the fight with all of it in place:

1. Summon your Imp (Summon Imp, ten seconds, no Soul Shard) and sacrifice it with Demonic Sacrifice. Burning Shadow lasts two hours, so do this before the boss.
2. Summon your Succubus (Summon Succubus, ten seconds and a Soul Shard). With both points of Master Summoner each summon is 4 seconds shorter and 40 % cheaper.
3. Cast Soul Link and Demon Armor, then Life Tap back up and let a healer top you off.

Send the Succubus in on the pull. If it dies, summon another Succubus. Summoning the Imp cancels Burning Shadow.

The Life Tap a second and a half before the pull that some fights' lists show is worth 0.0 %: you start the fight at full mana.

Priority

Each time your global cooldown ends, start at the top and cast the first line whose condition is true. The widget gives every line's casts and the damage you would lose without it.

The lines in order, with their reasons:

1. Mana potion and Demonic Rune once your mana is below 60 to 75 %, while at least 15 seconds are left. They have separate two-minute cooldowns, so you use both.
2. Searing Pain in the last few seconds. Its 1.5-second cast finishes where a 2.5-second Shadow Bolt might not. The line is worth 1.6 %.
3. Life Tap when you are nearly out of mana, below 5 to 10 %. You pay 424 health plus your Spirit and get that much mana back. On a three-minute single-boss fight the line is worth 25.0 %, because without it you run dry long before the end. On a one-minute single-boss fight it is worth 0.0 %: with a potion and a rune your mana lasts the minute.
4. Curse of the Elements if it's missing from the boss. It gives five minutes of 10 % more magic damage to you, your Succubus's Lash of Pain and every caster in the raid, and is worth 5.7 % of your damage alone.
5. A Bane. Bane of Doom does one hit a minute after it lands: 1,742 Shadow damage plus four times your spell damage. It shares the Bane slot with Bane of Agony. Cast Doom on the pull, recast it when it lands if the boss will live another minute, and keep Agony up for the rest. Agony's damage builds up over its 24 seconds, the last ticks the biggest, so let each one run out before you recast. On a three-minute single-boss fight the Doom line is worth 2.3 % and the Agony line 2.7 %. Doom needs a full minute, so one-minute fights use Agony alone.
6. Corruption before it runs out, worth 8.7 %. It ticks every 3 seconds for 18, and in Forever the ticks can crit.
7. Immolate the same way. It deals less per cast than a Shadow Bolt for the same 380 mana, so where mana is the limit it adds little: 0.6 % on a three-minute single-boss fight, against 3.3 % on a one-minute single-boss fight.
8. Shadow Bolt in every other gap. The line is worth 44.3 % and the spell is 43.8 % of your damage.

On one minute the build adds Shadowburn, an instant that comes back every 15 seconds. Cast it whenever it is up, and save one for the last second and a half if you can. Its two lines are worth 0.8 % and 1.7 %. Each cast needs a Soul Shard in game.

More than one target

Against three bosses the dots take over. Corruption and Immolate go on all three, Bane of Agony on the two you aren't facing and Bane of Doom on the main one. Shadow Bolt drops from 49.7 % of your damage on one boss to 10.2 % on a three-minute fight against three bosses. The three-boss fights in the picker show that build and rotation.

Cooldowns

Demonology has no burst to save. Talisman of Ascendance is used on the pull and again each time its one-minute cooldown is up. For 20 seconds every spell you cast stacks 40 more spell damage, five stacks at most. In game it also ends after your sixth spell, which our simulator doesn't apply, so it is a little weaker than shown. Bane of Doom's one-minute cooldown starts at the pull, and a Troll's Berserking goes out then too.

Weakness Analyzer's use, 5 % crit for 20 seconds or until your next crit that isn't a tick, isn't simulated, so its place in the set rests on its spell damage alone.

Cooldown	Uses	At
Talisman of Ascendance	1	0:00
Major Mana Potion	1	0:10
Demonic Rune	1	0:31

What your log should show

Line your Warcraft Logs casts up against this table. Shadow Bolts per minute is where moving or tapping too often shows first.

Ability	Casts per minute	Of damage	Crit
Shadow Bolt	14.1	43.8 %	17.3 %
Corruption	3.5	13.3 %	17.6 %
Bane of Agony	3.4	12.8 %	17.4 %
Immolate	4.2	9.6 %	17.5 %
Succubus: Auto attackpet	30.0	9.1 %	19.1 %
Shadowburn	3.9	8.1 %	17.8 %
Succubus: Lash of Painpet	5.0	1.7 %	17.2 %
Searing Pain	1.4	1.5 %	27.4 %
Succubus: Demonic Brandpet	–	0.0 %	0.0 %
Talisman of Ascendance	1.0	–	–
Life Tap	1.0	–	–
Curse of the Elements	1.2	–	–
Succubus: OtherActionManaGainpet	17.1	–	–
Demonic Rune	1.0	–	–
Major Mana Potion	1.0	–	–

Look for about 14.1 Shadow Bolts and 1.0 Life Taps a minute, Corruption on the boss 88.9 % of the fight, and your Succubus near 10.8 % of the damage. If your pet's share is far below that, check that it attacked from the pull and stayed alive.

Uptimes

Buff or debuff	Uptime	Times per fight
Bane of Agonyon the boss	92.1 %	3.0
Corruptionon the boss	88.9 %	3.0
Immolateon the boss	79.6 %	3.7
Ascendance	33.4 %	1.0
Ascendance	33.3 %	1.0
Shadow Vulnerabilityon the boss	31.3 %	2.1
Decimation	29.3 %	5.8
Demonic Brandon the boss	1.4 %	1.2

Burning Shadow, Master Demonologist and Soul Link should read 100 %. If any drops, your Succubus died or you summoned the Imp.

Shadow Vulnerability, from Improved Shadow Bolt's crits, should be up about 31.3 % of the fight.