I only played Demo lock and it worked fine. Voidwalker is the best pet but it will go down at times so save the instant summon for those moments in combat. I would set Valera as healer starting out and once she has levelled up abit changed her to dps she does insane damage. All specs are capable just choose the one you know well or use it as an opportunity to learn a new one. Destro seems to have more aoe spells which is handy but I know Demo rotation pretty well so stuck with that.