Spell hit first, then spell crit, then casting speed: on a one-minute single-boss fight a percent of each is worth 14.8, 11.7 and 9.04 Spell damage.
A point of Shadow damage is worth 0.86 and a point of Intellect 0.21. Each weight is in Spell damage, found by nudging one stat on the benchmark set, so it prices the next point on top of that gear.
Per point
- Spell damage1.00
- Shadow damage0.86
- Intellect0.21
- Fire damage0.12
Per 1 %
- Spell hit14.8
- Spell crit11.7
- Casting speed9.04
Spell hit
Until Blizzard publishes Forever's spell table our simulator keeps Classic's. A raid boss shrugs off 17 % of a hitless warlock's spells. Each percent of hit takes one off, down to a floor of 1 %, which you reach at 16 % hit. This set has 4.0 %, from gear and 
Suppression, which leaves a long way to the cap. The Succubus copies your spell hit onto Lash of Pain and its melee, so each point lands twice. In Forever an item's "chance to hit" applies to your spells.
Spell crit
A Shadow Bolt crit does double damage with 
Ruin, not 150 %, and starts 
Improved Shadow Bolt's 20 % Shadow bonus for 12 seconds.
Your Succubus inherits your crit as well. The sheet shows 17.4 %, and nothing caps it. Intellect adds 1 % crit for every 60.6 points, and Humans get 2 % from Sword Specialization while they hold 
Sageblade.
Spell damage, Shadow damage and Intellect
Shadow damage counts for 0.86 against plain spell damage's 1. Immolate and Searing Pain don't use it, and the Succubus copies a tenth of your spell damage but ignores Shadow-only bonuses. Fire-only damage barely matters, 0.12. Intellect buys mana as well as crit, so it rises with the length of the fight: 0.21 on a one-minute single-boss fight, 0.61 on a three-minute single-boss fight. Spirit is worth 0.18 against one boss for three minutes, partly through Life Tap, which adds your Spirit to every tap.
Casting speed
Casting speed shortens your Shadow Bolt cast and your global cooldown alike. The pre-raid pool has little of it: the gloves' Minor Haste enchant, 1 %, is the only source in these sets, and Wowhead marks it as test-realm only.
On every fight
Hit leads on one boss at every length, and crit is close behind. On three bosses both read lower against spell damage: 9.13 and 9.51 on a three-minute fight against three bosses, with hit and crit about level.