Dimeritium Shackles vs Dimeritium Bomb

I'm using a mulligan ST deck and because of a combo I have going on I can't use the dwarf cleaver. Before I had shackles and it felt like I was holding onto it all game with few targets or when I could demote something I needed a second card to take it out (things like Kayrun, vampire elder, Tiber, etc) so I replaced shackle with a bomb and so far it feels like I've been doing better with it.

Am I missing something? what are the vital lock targets? It feels like most minion effects happen before they get on the board. But most decks include a lock.

Should I just toss in a shackle anyway? My deck is already at 29 cards however I try to only play 24 of them. For a visual here is the deck list. The wardancers, roach, and zolton I try to summon from my deck or otherwise mulligan.