Sure it's doable and playable. Warlock is can be tricky to make macros for the dps rotation, but I have a mixed-class team with a demo lock who does respectable damage using only 2 buttons. You can use the cooldowns of Call Dreadstalkers and Soul Strike in a castsequence to ensure you have enough shards for Hand of Gul'dan. The second button is for when you have demonic cores. You can make a big weakaura to show when to use this, so that you will notice it even when you are focused on your main.

As well as /follow you can use interact with target in combination with click-to-move. There is also a multiboxing addon called EMA that will do (among other things) follow-strobing so the lock will automatically move to your main after combat.