loverdrive
Prophet of the profane (She/Her)
This is a very valid concern, though I've taken steps to address it.5e doesn't try to control "big attack" vs "multiple small attacks" as an important balance difference. (most, but not all, damage boosts are "per turn")
Making it matter seems risky.
Magic Missile, for example, makes force vulnerability crazy dangerous.
It also impacts melee/caster balance. Melee characters are more likely to rely on multiple taps, while a caster is more likely to have a big attack; the caster often also has some multiple tap options.
There are pretty few monsters that are resistant to physical damage (well, there aren't many monsters that have resistances at all) in my book. For the reasons you've outlined and also because dealing more damage with, say, Bludgeoning has pretty much the same effect as dealing less damage with Slashing and Piercing, but just feels more satisfying.
That's mostly for spellcasters, as they actually have an option to make one powerful attack vs several weak ones -- like Scorching Ray or Flaming Sphere vs. Fireball.By making having that choice -- single vs multiple -- important, you weaken weapon users. The "consequence" of an attack roll landing is bounded in 5e, which also effectively bounds damage (rogues and paladins are the exception to that rule) per tap, while the "consequence" of a save failing is unbounded (up to and including "lose the fight").
If I were redoing everything from scratch (which I won't, I already have two systems I'm working on and not much energy and free time), I'd want to have things like All-Out attacks or somethin available for martial classes, but, again, I won't.
That something that sounds cool, but still, one of the main reasons I want to ditch x2 vulnerabilites is because I suck ass at numbers. Maybe I'm retarded, but even multiplying by 2 is a hard time for me, multiplying thing by 1.5 is gonna just fry my brain.Consider using half-vulnerability: weakness; +50% damage instead of x2.
x2 runs into the problem of being too big. 50% is big enough to track without dominating, and is pretty fast math.