There is a way to speed up printing on HP Laser Printers by changing a print setting. This may also be possible on other brands of MFP's but it has only been tested using the HP Universal Printing PCL. The setting could be similar.
All you need to do is go to Devices & Printers on the local computer (Print Server if you use one), right click the printer that is printing slow, and click printer properties. This will bring up a dialogue box, if you go into the 'Advanced' properties -> Printing Defaults. This will open another dialogue box, again go to the 'Advanced' tab.
You will be presented with several options, one of which is the Graphics Mode. By default this is set to 'Send Graphics As Vector' this isn't too good for laser printers as they print with pixel data so some prints would need to be converted by the printer before it can print. If you change this setting to 'Send Graphics As Raster' then the printer won't need to convert anything and print speeds will be improved dramatically.