FreeKaner
Prophet of the Dumpsterfire
Integer based scaling can't give fractional values, whereas 3% of 15 damage gives you less than half a point of extra damage.Sawyer's light shines so bright it blinds those who dare gaze upon it with disdain. That's why they think +1 on a 1d20 roll isn't a percentage increase because it's a flat number.
But yeah, you can express the output as a percentage if you wanted, although that's a bit pedantic. Multipliers can be pretty dodgy in general and viewed from two different perspectives they can skew progression rewards. Either by accelerating them too quickly at the high end; such as stacking weapon buffs in Tyranny, or in modern Blizzard games; or by providing no noticeable difference at low values until you stack enough of it that you risk tilting your end-game towards the former. Personally I prefer the latter more conservative approach, and +5% to shadow damage, for instance, is narrow enough that further increases won't immediately begin scaling the games numbers by powers.
I think dps values are always less interesting than flavour, however, because they can't be leveraged by the developer in cases of special exception. For instance, like Junta mentioned before; it's satisfying that the Paladin in particular has a weapon tailored to themselves that better enables their prime-motivation in smiting evil and that you loot it from an evil dragon, no less. Although I disagree that it required any particular foresight from the developers when the flavour is intuitive to naive gamers. It would be like including dwarves but not warhammers, otherwise.
I don't disagree with the whole premise of balancing done by flavour than simply increase in numbers, soulbound weapons in WM and uniques added later in PoE a step in right direction, but the core of the argument about percentage increase is pedantic at foundation.
A flat increase or percentage increase on a damage, health or any other flat number is essentially the same, the only difference is based on perception where +20 health can feel more solid and tangible than 5% increase which may be more but feels less significant especially when the percentages all add up together somewhere.