Refine the loop to only scan through the drawn boundaries that are being tested against (except when skipping cull). This eliminates a huge bottleneck / lookup time from the original loop each frame.
The update should affect tilemaps exponentially based on their size. It reduced my culling time to 1/70th for 1000x1000 tilemaps, and by about 1/20th on 250x250 tilemaps. It also reduced my requestAnimationFrame time from over 16ms per frame to ~1ms for the larger map.
The fix from https://github.com/photonstorm/phaser/pull/3354/ leads to some tiles getting culled when camera is zoomed as the camera.scrollX/camera.scrollY-Properties are needed in unscaled Coordinates (World-Coordinates?) in CullTile.js
Error gets bigger with distance from (0|0)