The main reason for Odyssey to use Guardian PD is player does not have enough Autopulse/Plasma Cannon for all ships, and Odyssey gets stuck with the leftovers (i.e., Guardian PD). I have used Guardian PD/Reapers/IR Pulse Lasers on Odyssey before, when all of my available autopulse/PCs went to my Sunders and Apogees (those who cannot use Guardian PD effectively at all due to hardpoints). It is not the most effective configuration for Odyssey, but it works.
As for Paragon, it can destroy any enemy ship with Heavy Blasters alone in all medium mounts. Large and small can be whatever the player wants. Back when charges were always expended at anything, it was fun holding fire then turn it on for all burst/guardian PD to kill one target. After the fireworks, hold fire again, then activate for more beam spam. Now that burst PD only shoots when at max charges, this does not work anymore.