the only i one i put any faith in the holocaust... hammerhand is neat in that it doubles your base strength, but for say an inquisitor it isn't as usefull because you only go to S6. (so it's less usefull than melta bombs + acolytes and/or combat servitors are in the anti-tank department)
scourging is too random for my tastes... if i want randomness then i'll go play orks or skaven!
the others are all daemon-orriented obviously!
i'd simply stick to holocaust as it's really all you need. a pie-plate in the assault phase is dead handy!
cheers!