In short, my Belief s that either The Guardians liked roasting in their own ships or humanity has disgraced their tech beyond recognition....
reason being is that these modules ( Guardian Power distributor and PP) are not exactly as top of the line as our human ones, in fact both of these can be trumped by engineer upgrades alone. in the scenario of the PP, yes the guardian one does have a higher power capacity, but Human PP can be engineered to comfortable ranges and still not have THAT much heat!!! 0.1 extra is a big number to a person who like to keep things frosty..... fire railguns twice and we have ourselves a barbeque!
Power distributor much the same, go for engineered grade 5 rapid charge plus the special effect with additional charge already surpasses that of the guardian one. capacity may not be as much I think, but with rapid charge you can out charge the power used and shoot forever completely outdoing capacity.
The power boost is just a gimmick but an interesting one (in that future guardian modules may indeed link boosting overall ship stats beyond engineers). when I heard this thing also generates 'more' heat I cried a little and lost interest immediately. pair this up with the Guardian PP and it would be interesting to see if you can take off without spontaneous combustion.
Guardian FSD Booster on the other hand looked alright, but will be re-released next major update. If only we had a way to counter the heat (like an inbuilt Guardian heatsink) that could reduce the excessive heat generated by these modules, then they would be well and truly worth wile!!