Yeah I've played with direct laser exposure of cyanotypes, and have also gotten some good results with area exposure through a transparent LCD screen.
The thing with laser exposure is that it comes down to two things, speed and power.
If you want the dots to be so small as to be invisible (on the order of 30 to 50 microns probably) then you need a lot of dots, and if you want the print to be done at any reasonable speed you need hardware that can 'write' those dots extremely fast, like on the order of a few hundred thousand dots per second if you want a reasonable sized print to be done in less than a few hours.
And if you're 'writing' dots that fast your exposure time is in the microsecond range, so you need to get enough UV power onto the paper to fully expose your chemistry in that length of time. My LCD screen exposure unit puts approximately 30W of UV power onto an A4 sized piece of paper for an exposure time around 4 minutes. Unless your laser source is also 30W of output power, it will take longer to expose that same area with the laser, but most cheap available UV laser diodes have an output power of between 500mW and 1.5W, which means that the laser would either take MUCH longer, or you'd need to use at least 20 laser diodes in parallel to get the same exposure time. That's why if you look at those Luscher machines they talk about a single machine having up to 128 laser channels, that's how they can get a reasonable exposure speed.
It's similar to an inkjet printer, the print head actually has many nozzles per colour channel and writes a 'stripe' of ink across the page, imagine how long it would take if the printer only had a single tiny nozzle per colour and had to scan the head back and forth tens of thousands of times per print. I'd imagine you could do the same thing with lasers (have dozens of laser diodes writing a stripe of print at a time) but I decided that project was probably going to be too costly and time consuming for me and I was getting better results with my LCD screen unit.
