How are other organizations structured to support HRIT systems?  Looking to move from a decentralized model where HRIT sits in HR to a centralized within the larger tech org and want to learn from others on the latter.

I would suggest a model where the admin and super user aspects are within HR, and the technology components managed within an IT Operations group.

This allows you to provide proper support thru your service desk, and other IT Teams while sharing resources across applications.

We are still using a centralized model. We find it to be most efficient given our relatively small team.

We actually went in the other direction. We were using ADP, and I had the system administrators working in my group. However, after a large change in systems, we moved the roles to report to HR. It made more sense, as the work they were doing daily directly impacted the HR teams. They are in their staff meetings and strategy conversations. They can support the organization more effectively as they are tied directly to that team. We still maintain a connection to them and help where needed. We partner to evaluate technical skills as necessary. However, I'm a proponent of the resources being on the teams they support where possible.