In 4E, with baseline 60% PC hit rate and monster 40% hit rate, a +1 level on a monster (with no other stat changes - same HP, damage, etc) makes it 60%/55% tougher and 45%/40% deadlier, or about 23% more dangerous. Every 4 levels this is enough to scale monster danger by 2.3x - basically, the majority of the XP scale comes from ATK/DEF, not HP and damage.
The level gradient at low levels is far steeper, because monster HP scales with (L+3) and damage with (L+8) - a level 5 monster has +4 ATK, +4 DEF, x2 the HP and 44% more damage output than a level 1 monster. This was a flaw in 4e monster math; the XP table basically doesn't account for HP/damage changes!
And past low levels, the range of monsters you fight have basically no changes in HP/damage. At level 20, a level 23 monster has +30% HP over a level 17 one; at level 5 +/-3 level foes differ by 120% HP! Damage wise it is even flatter.
But if you leave the +/- 4 level sweet spot, combat becomes auto-hits and wiff-fests, and +ATK bonuses get even better than they are. (ATK bonuses are sleeper powerful; making them even stronger makes the game worse).
This honestly makes high level 4e combat get a bit snoozy. A level +4 monster is harder to hit and hits more often, but isn't more threatening; thus elites and solos. But they boost HP more than they do damage, so we get high level low-risk combat feeling.
4e XP expects monsters to get 2x tougher every +4 levels. If we flatten ATK/DEF to +1/2 levels (lots of ways to do this), and we kept the same XP tables, we'd have to take a look at both player and monster HP/damage.
Now a level X+4 monster is "worth" two level X monsters in encounter building. Those two level X monsters get killed one by one. If you take a monster with half the threat and half the toughness and make 2 of them, you actually end up with closer to 75% of the threat of the bigger monster.
We can get a decent approximation of this this by taking (threat) * (toughness) and taking the 1.6th root - for triangular numbers in the 1-5 range it is very accurate, and good enough beyond that.
So if we want a X+8 monster to be worth 4x the XP, it needs 4^1.6 = 9.2x times the total threat volume. A +4 ATK/DEF boost (+level/2) contributes 2.3x, leaving a 4x factor in HP and DPR that needs to be made up.
Ie, every 8 levels, x2 HP and x2 DPR, or 1.4x every 4 levels.
We'll take level 5 as our baseline. So 64 HP and 13 DPR.
L 1: 9/46 (compare with 8/32)
L 5: 13/64
L 9: 18/90 (compare with 17/96)
L13: 26/128 (compare with 21/128)
L17: 36/180 (compare with 25/160)
L21: 52/256 (compare with 29/192)
L25: 73/358 (compare with 33/224)
L29: 104/512 (compare with 37/256)
As you can see, this first principles 4e monster design agrees with monsters in heroic, but starts divering in paragon. Monster HP stays similar in paragon, but damage starts climbing significantly.
Baseline 4e monsters go from 18 to 28 damage over paragon, or +5% per level. We basically want to double this percent-per-level.
Baseline 4e monsters go from 28 to 38 damage over epic.
Now, if you do this, you also need to tweak PCs
or lower the number of expected foes they can handle at a given level.
Keeping track of exponential curves is annoying. And we can make it piecewise linear to simplify it.
Heroic remains (8+L) damage and (3+L)*8 HP baseline.
For Paragon, level 10 is 18 damage and 104 HP. We want to hit 43 damage and 250 HP by level 20; that is +25 damage and +146 HP.
L 01-10 Heroic: L+8 damage, 24+8L HP (9 to 18 DPR, 32 to 104 HP)
L 11-20 Paragon: 2*L damage, 16L-50 HP. (22 to 40 DPR, 126 to 270 HP)
L 21-30 Epic: 5*L-50 damage, 25L-250 HP (55 to 100 DPR, 275 to 500 HP)
L 31-40 Legendary: 15*L-350 damage, 75L-1800 HP (116-250 DPR, 525-1200 HP)
and that should make monster threat ratios remain very high; higher level monsters will feel scary not just because of wiffs, but because they have a lot more damage and HP.
For PCs, strip half-level bonuses. It also requires some boost to PC damage and durability in paragon and epic levels.
1. Double your per-level HP increase in paragon, and 4x it in epic. So a fighter gains +6 HP/level in heroic, +12 HP/level in paragon, and +24 HP/level in epic; a 20 con level 30 fighter has 20 + 9 + (10*6) + (10*12) + (10*24) = 449 HP (comparable to a level 30 normal monster!).
2. Increase damage output of powers:
- At-will powers do 2 dice of damage at level 11+ and 3 dice of damage at level 21+
- L 10-19 powers have their damage dice x2ed
- L 20-30 powers have their damage dice x5ed
Now the downside... the numbers just get too big. If you thought high level 4e was buckets of dice before, we are talking Exhalted RPG buckets of dice now.
So we have to roll stuff back; the power gradient can't be this steep (reconstructing 4e standard encounter building) with flat ATK/DEF curves (allowing for a wider range of foes to be in the zone of validity). The buckets-of-dice came from the fact that we need a monster 10 levels higher to have 2.4x the HP and damage, and if you repeat this 3 times off a monster that starts with 10 damage and 30 HP, you get 140 damage and 400 HP.
Another approach is to extend the window of viable foes and change the XP curve as well. The window of viable foes is limited by the scaling of ATK and DEF (within +/- 4 of "evenish") - if monster ATK/DEF scaled at +1/2 from level 1 to 10, but then slowed down at higher levels, the window opens up. That in turn allows monsters with a wider range of HP and DPR to be selected
without exponential scaling of numbers.
We can even do this while keeping PCs relatively unmodified (ie, strip the half level, but not much else); nothing requires that monster ATK/DEF scale exactly like PCs do, so long as the rules for building encounters are simple.
OTOH, doubling the damage dice of paragon tier and above powers is a great improvement to the game; 4e didn't scale PC damage dice fast enough as published, leading to multi-tap attack spam.
So as a compromise, what if monster ATK/DEF scaled at +1/2 level in Heroic, +1/3 level in Paragon, and +1/5 level in Epic?
PC assumed attack is (3+L) in baseline 4e. Monster AC was 14+L, and PCs hit on a 11+. Viable foes could be hit from 7+ to 15+. So 10+L to 18+L AC are "viable" foes, which corresponds to L-4 to L+4 foes in baseline 4e.
We change accuracy to be about (3+L/2).
L1: +3; viable monster AC is 10 to 18
L11: +8; viable monster AC is 15 to 23
L21: +13; viable monster AC is 20 to 28
L30: +18; viable monster AC is 25 to 33
Monster AC is changed to 14+L/2 in Heroic (14 to 19), 16+L/3 in paragon (19 to 22), 19+L/5 in epic and legendary (23 to 25 epic, 25 to 27 legendary)
L1: Viable foes are Heroic (+/- 10 levels)
L11: Viable foes are Heroic or Paragon (+/- 10 levels)
L21: Viable foes are Paragon, Epic or Legendary (-10 levels to +20 levels)
L30: Viable foes are Legendary
pfah, this is tricky.
If we can shave off a few more +bonuses to ATK and DEF on PCs it could tighten up. Like, cut masterwork light armor, and drop masterwork heavy armor to +2 AC per tier (shaves off 2 AC off every PC), halve enchancement bonuses down to +1 per tier (shave 3 ATK and 3 AC and 3 NADs). (Honestly, NADs are already bad enough).
That should be enough that +/- 10 levels is a valid foe range from level 1 up to 30.
...
Gotta zzz. I enjoy this, hopefully someone will enjoy reading it.