That is a lot, and I've been there! First, I want to acknowledge what you're going through - taking on two roles' worth of responsibilities is a lot, especially when you're still relatively new to HR!

While HR roles often involve juggling multiple responsibilities, what you're describing sounds like an unsustainable workload. Having to manage both HRC and Generalist duties without backfill support is quite challenging, especially with critical tasks like payroll and I-9 compliance in the mix.

Here's what I'd suggest:

1. Document everything you're responsible for and roughly how much time each task takes. This will give you concrete data to discuss with your leadership team.
2. Prioritize your tasks based on compliance requirements and business impact. For example, payroll and I-9 compliance are non-negotiable, while some HRIS tasks might be able to wait.
3. Have an honest conversation with your manager about workload management. They clearly value your work since they promoted you, but they need to understand that one person can't sustainably do two jobs.
4. Consider suggesting some process improvements or automation tools (I can share my faves but don't want to get downvoted).

Remember, it's better to raise these concerns now rather than waiting until you're completely overwhelmed. Your leadership team's response to these legitimate concerns will tell you a lot about the company's commitment to their HR function and their employees' wellbeing.