Rules
From the Player's Handbook:
High Jump. When you make a high jump, you leap into the air a number
of feet equal to 3 + your Strength modifier if you move at least 10
feet on foot immediately before the jump. When you make a standing
high jump, you can jump only half that distance. Either way, each foot
you clear on the jump costs a foot of movement. In some circumstances,
your DM might allow you to make a Strength (Athletics) check to jump
higher than you normally can.
p. 182
Falling
A fall from a great height is one of the most common hazards facing an
adventurer.
At the end of a fall, a creature takes 1d6 bludgeoning damage for
every 10 feet it fell, to a maximum of 20d6. The creature lands prone,
unless it avoids taking damage from the fall.
p. 183
Step of the Wind
... Your jump distance is doubled for the turn
p. 78
Jump
... the creature's jump distance is tripled ...
p. 254
Combining Magical Effects
The effects of different spells add together while the durations of those spells overlap. The effects of the same spell cast multiple times don't combine, however. Instead, the most potent effect - such as the highest bonus - from those castings applies while their durations overlap.
p. 205
This last gives several interesting possibilities for how these combinations actually work - but that is another question.
Definitions
Giving "jump" and "fall" their common English meanings (1.b & 2.b being the most appropriate), they are not the same thing. Jumping is voluntary and in control, falling is involuntary and out of control. So the first does not automatically lead to the second to my mind.
Designer Commentary
In addition there is this quote:
@Plaguescarred Can you jump farther than your movement when using
magic i.e spell Jump & boots of striding and springing?
@mikemearls
i'd rule yes - design intent is to make you jump super far
Read more: http://www.enworld.org/forum/showthread.php?362742-Jump/page2#ixzz3SirpzT8U
So we can draw two things from this:
- It's at DM discretion (what isn't)
- There's magic involved.
Discussion
Naked Jumping
Starting from the basics, a PC can jump up 3 + Strength modifier, without magic this is a maximum of 8' - so there are no falling considerations. A monster or magiced-up PC with a Strength of 24+ or a thief with Second Storey Work and high enough Strength and Dexterity can jump into the danger zone (>10'). I would argue that if you are strong enough to jump that high, you have the muscle strength to absorb the shock of landing without damage. There is some simple physics involved here - the speed at which you leave the ground equals the speed that you return - if your leg muscles can generate that speed then I say they can absorb it.
As a side note, I would rule that you can safely jump down less than 10' or equal to your maximum high jump whichever is the greater. Oh, and they wouldn't need a run to jump "straight" down. If you are jumping across a chasm to a lower ledge, I would rule that the so long as the total drop from high point to low point did not exceed this falling would not be a consideration.
Step of the Wind
A monk with Step of the Wind can double these heights. A 5th level monk wouldn't take damage from a fall like this anyway. For lower levels, as this is a specific class feature with a cost; I would be disinclined to nerf it.
Jump Spell
Jump can be cast on anyone and takes the maximum of a very strong PC to 24' and monsters to 36'. I cannot accept that this 1st level spell is intended to give the PC the power to jump up in the air (to whatever height) and then come down by falling to their death. This is simply not credible, particularly when you take into account the designer's comment on how he sees the spell being used.
The Combination
Wow! What a great idea the PC had! Of course you don't take falling damage and have some inspiration while you're at it!
This is a progression to level 11, involving 4 classes. Vivisectionist Alchemist grants sneak attack, a mutagen to improve Dex as well as opening up discoveries(to take an additional limb to allow for reloading of firearms. Urban Barbarian allows for rage to improve Dex rather than Str/Con. Weapon Master Fighter aids in the protection of the weapon as well as providing additional bonus to hit and damage.
The benefits of increased attacks vs True Grit, are somewhat difficult to ascribe numerical values to, however(assuming a minimum dexterity of 34 which is what is likely to be had with this build design, and only a +1 weapon enhancement within the 30 Point-Blank requirement), each additional shot will be doing 1D8+20 average damage 25/max 28. The average of 5D6 is 18/max 30.
- Gunslinger: Point Blank Shot
- Gunslinger
- Gunslinger: Precise Shot
- Gunslinger: Rapid Reload
- Gunslinger: Rapid Shot
- Alchemist(Vivisectionist)
- Alchemist: Discovery: Extra Arm/Tentacle + Deadly Aim
- Barbarian(Urban)
- Fighter(Weapon Master): Two Weapon Fighting + Improved Two Weapon Fighting
- Fighter: Cluster Shot
- Fighter: Weapon Focus
Best Answer
Just Cast fireball A Lot
A sixth-level sorcerer has three third-level spell slots and six sorcery points. That sorcerer can get ten more sorcery points by converting their lower-level slots, and then convert ten sorcery points into two more third-level spell slots. (We assume the sorcerer has a few rounds of downtime to do this before the battle.)
The sorcerer then can cast fireball five times, once per round, for an average damage of 28 before saves.
The sorcerer can apply Empowered Spell to each of their casts. This lets them reroll up to four damage dice. The average damage goes from 28 to 33.61 (according to my simulation). Then, using Draconic Fire Bloodline, they can add their +4 CHA mod to the damage roll, for an average damage of 37.61.
A bear has a +0 DEX save, versus DC15, so it passes 30% of the time, which multiplies the damage by 0.85. We multiply by four bears, and we get 127.8 damage per round.
If our race is tiefling, then we can also cast hellish rebuke once for 3d10*.85*.2=2.8 damage per round. The total is 130.6 damage per round.
Can some other build do better?
I think sorcerer is the best class for this, simply because the sorcerer is the only class that can cast five fireballs at this level. Multiclassing would worsen the build because it would lose the Elemental Affinity power which requires six levels of sorcerer.
I did not investigate other sorcerer options -- I just took the one that was visible on https://roll20.net/compendium/dnd5e/Sorcerer (Draconic with Fire), as it offered an additional +4 fireball damage and that seemed like a good deal. It may be possible to do better using some other choice.
It's unfortunate that the sorcerer doesn't have a good damage-over-time spell to supplement all the fireballs, perhaps making use of their concentration or their bonus action or their reaction. Unfortunately I didn't see anything promising on their spell list.