Load Balancing between On-Prem server and Azure Cloud server

I would most certainly do this with F5 DNS (the artist formerly known as GTM) or F5 Distributed Cloud DNS, even better. WAY cheaper. 

The great thing about the Distributed Cloud option is that it uses Anycast from 22+ PoPs globally to drive traffic to the single IP address. From there, you can easily LB between your DC front door VS and your EIP.  It took me 20 minutes to do this on my first attempt after taking a 1 hour training on it.