Well, you just have to do it in one go. Being efficient with the space you have is something that has worked in previous patches before.
Some tips:
Since Totems don't die anymore, you can use AOE to clear the Groupies while still fighting Laz.
Corners and such can be useful so squeeze out that last bit of Purify time to make it.
If you stay about half screen or so away, Laz does not teleport so much and you can circle him back and forth for a bit and keep hitting Purify.
You could try if slow enemy% helps. It makes it so if you hit Laz with it, he's just generally slowed down, which makes the fight easier in almost every way.
Gradually taking small steps in a zigzag pattern can help save more space in the corridors.
Here's an old video someone made:
Pls post when you've done it!