Semantic document search is one of the core use cases we see in the community (besides Question Answering) and Haystack was pretty much started because we saw that you need much more than just models. It's so much pain to integrate models properly with document storage (e.g. elasticsearch), route requests effectively in larger pipelines or track user feedback in production. Have you tried using DPR or sentence transformers for your case?

Disclaimer: I am one of the maintainers of Haystack:)