Daranharuk

I'm a WoW noob and English isn't my first language but I'm a bit confused about the ability priority list. When done with the opening sequence I'm left with 0 soul shards, right? So....I can cast Doom and Summon Darkglare and then I have 0 soul shards again? I'm sure that it is me doing something wrong. Can someone explain to me (without calling me an idiot :P ) what I do wrong, please.

I have a (probably stupid) question about the single target rotation. English isn't my first language, so I'm having a hard time understanding some parts of this guide. My fault, not yours :-) Why do I need to have (under some conditions) a trinket proc or Dark Soul: Misery up, before casting Haunt ?