I'd still do this.

Security isn't one thing, it's layers. So if any single layer fails another still prevents access.

With just Tails, if a bad actor gets access via a compromised user machine, they could potentially get access to the rest of your network. If the server is on an isolated Lan, there's nothing for them to access - it's a rock-solid guarantee that the most they can do is damage to that server and network segment.

We (us IT folks) see users get compromised almost daily, largely through social engineering. It's a huge risk.

And it's trivial to have something on its own Lan segment.