I went 8 into demo for improved voidwalker and then all into affliction until 40. Then I'll respect for soul link. Affliction offers more in the intermediate levels.

Also, I recommend farming BRD for https://classic.wowhead.com/item=222...-eternal-light

There are mobs in Scholomance (that you'll be farming a LOT as a warlock comp) that are immune to all magic types except holy. This wand is the only wand in the game that does holy damage and, combined with the physical damage from your warlocks, will help you kill them.