Well the 'bulk' might be in the width as it's a few mm wider than the X-T2 with a little bit bigger grip, but that's the hardly bulky even with the grip. Anyway most serious video shooters will rig a camera so you are only really using the sensor to output to an external recorder. The grip has the headphones out and increases the record time to 30mins in one go. Really if you need to be recording video, seriously, get a real video camera. For basic situations and most shots 10mins of record time is loads. Depends on the application.
Full frame sensors ISO performance are good these days but not a patch on the GFX so if you need to shoot as 12800+ iso and get clean files with outstanding IQ that is where you should be. The GFX kills it over the FF cameras in that regard.
Canon 5Div is 800g without battery and card.
Fujifilm X-T2 is 507g with battery and card.
And lets not count the much bigger glass penally of full frame. For example the EF 35mm f/1.4 is neatly twice the weight of the XF23mm 1.4. So I'd fairly say that the Full frame cameras and lenses needed for a shoot are a lot heaver than the Fujifilm system. A LOT!