Filoni has gotten a lot of things wrong lately with rebels. My son is a big fan of the clone wars series and the first thing he said to me is dad, "why are the sabers so thin and pointey? He also mentioned that the storm trooper lasers looked lame compared to the clone wars seasons. I would agree.
Season 2 rebels episode 2 miffed me the most when captain Rex fired his blaster and it was a bright blue laser with a clearly defined white core to it. (As if we were back to the clone wars). Then it was back to the boring red lasers again with the storm troopers. Not only are the lasers flat and boring, but they do not properly reflect environmental light as they did in the clone wars.
I am not going to buy Filoni's bullshit that "the technology was simply lost over the years (in the star wars universe). It's more of the lack of vfx from the original trilogy at the time. And Filoni is trying to recreate a look from dated special effects technology. (80's star wars ect). Over All SW Rebels is not doing as well in regards to TV ratings that the clone wars did. One could argue that the art direction was a big part of this...
Take a look at Star Wars battlefront and the stormtroopers lasers look as they did from the clone wars.
My point of all this is that this is an intentional Filoni "baloney" decision. One that never would have been approved if he was back still in the skywalker ranch. George Lucus would not have approved of that decision as he was heavily policed in the Art direction of the clone wars.
Now since George sold his sole to Disney we will be looking at a lot of questionable art directions any future Star Wars related content.
I am willing to fix the light sabers for rebels, but I do not have enough time to fix the lasers. For my son well... He is going to have to work on his suspension of disbelief...