Are heavy bolters decent?

I was thinking about either including a dakka pred or a squad of havocs with 4 heavy bolters in my army because I like hoolding big fistfuls of high strength dice in my hands, and was wondering if they are a viable option over say plasma weapons or reaper autocannons for my budding Chaos Army. As a former tyranids player I was always quite terrified of heavy bolters since they would mow down my carnifexes with ease, but that was 4th ed and I am really not sure if they are decent vs all opponents or not. All of my friends scoff at heavy bolters as useless but I think they have potential and I wass hoping that I am not the only one who thinks this. Thanks in advance!