Measured on a one-minute single-boss fight: 12.3 Spell damage for each 1 % of spell crit, 11.1 for 1 % of spell hit and 7.72 for 1 % of casting speed. Shadow damage comes to 0.85 a point and Intellect to 0.52. The unit is a point of Spell damage, added to the benchmark set.
Per point
- Spell damage1.00
- Shadow damage0.85
- Intellect0.52
- Mana per 5 s0.16
- Fire damage0.13
Per 1 %
- Spell crit12.3
- Spell hit11.1
- Casting speed7.72
Hit
Before any hit, 17 of every 100 spells you cast at a level-63 boss miss, and no amount of hit takes that below 1, so the cap sits at 16 %. 
Suppression gives 5 % and the set's gear brings you to 9.0 %, so you still miss roughly one spell in eleven or twelve and every point of hit counts. Your Succubus inherits your hit. Forever hasn't published its spell table, so the 17 % is Classic's.
Crit
Your crits deal double damage instead of one and a half: 
Ruin does that for Shadow Bolt, Immolate and Searing Pain, 
Pandemic for Corruption and the banes, and Forever lets dot ticks crit. Hit and crit are separate rolls for spells, so crit never runs into a cap. This set shows 17.7 %, plus 5 % on Shadow spells from 
Malevolence, and your Succubus inherits your spell crit too.
Shadow damage
Shadow damage is worth 0.85 of a point of spell damage. Immolate and Searing Pain are Fire spells, and your Succubus inherits a tenth of your plain spell damage but none of your Shadow damage.
Intellect, Spirit and mana
Every 60.6 Intellect is 1 % crit, and each point adds 15 mana. Each point of Spirit adds a point of mana, 1.2 with Improved Life Tap, to every 
Life Tap, but Life Tap already makes mana cheap, so Spirit (0.12 on a three-minute single-boss fight) and mana per 5 seconds (0.27) count for little.
Casting speed
Haste shortens Shadow Bolt and your global cooldowns but not your dots' ticks, so it counts for less on three bosses, where the dots do most of the damage: 6.15 against 8.14 on one boss.
On every fight
Crit leads on every fight, then hit, then casting speed. Against three bosses every weight shrinks next to spell damage, because Corruption's ticks add up to 1.2 times your spell power and Bane of Agony's to 1.6. The three-boss tables also give spell penetration 0.80 a point, against bosses with no resistance for it to remove: treat that as a quirk of the simulation, not a stat to gear for.