Yamigawa (producer) said Bloodborne's "total game volume"
is greater than Demon's Souls, which is shorter than Dark Souls (30 vs 50 hours) but absolutely
nothing to sniff at. They may also not have compared it to Dark Souls due to their policy of never mentioning their dishonored multiplatform son near Bloodborne.
Yeah, Demon's Souls is a lot lighter. I'd imagine that this is closer to vanilla Dark Souls in size, so around 20 bosses and 25 "zones" (which itself varies wildly in size and diversity). This is not a small game, and there are essentially no cutscenes inflating that game time. A two minute video isn't going to spoil much of note unless it is literally a montage of every boss fight stitched together.
Demon's Souls was "low budget". Now that the companies know that FROM's dungeon-crawling "series" has an international audience, they wont skimp.
It's interesting that guns can be viewed as the spells. Bullets are like Arcane arrows, Shotguns and Flames are like Pyromancy. Limited ammo that you can refresh, etc. Different gun types use different stats, perhaps?