The following is roughly true for Challenge ratings on average. It should probably be true for player character Levels as well. The Proficiency bonus is the same for both Challenge and Level. Meanwhile, it probably makes sense for player characters to acquire the very high Ability bonuses sooner (Strength, Intelligence, etcetera).
Level | Proficiency | Highest
Ability | Attack
=
Proficiency
+
Ability |
| | | |
0 | +1 | +3 | +4 |
| | | |
1 | +2 | | +5 |
2 | | | |
3 | | | |
4 | | +4 | +6 |
| | | |
5 | +3 | | +7 |
6 | | | |
7 | | | |
8 | | +5 | +8 |
| | | |
9 | +4 | | +9 |
10 | | | |
11 | | | |
12 | | +6 | +10 |
| | | |
13 | +5 | | +11 |
14 | | | |
15 | | | |
16 | | +7 | +12 |
| | | |
17 | +6 | | +13 |
18 | | | |
19 | | | |
20 | | +8 | +14 |
| | | |
21 | +7 | | +15 |
22 | | | |
23 | | | |
24 | | +9 | +16 |
| | | |
25 | +8 | | +17 |
26 | | | |
27 | | | |
28 | | +10 | +18 |
| | | |
29 | +9 | | +19 |
30 | | | |
31 | | | |
32 | | +11 | +20 |
| | | |
33 | +10 | | +21 |
34 | | | |
35 | | | |
36 | | +12 | +22 |
| | | |
37 | +11 | | +23 |
38 | | | |
39 | | | |
40 | | +13 | +24 |
Notice, if true for players: a character who uses the feats for Ability improvements, will be able to attain +5 at level 8, +6 at level 12, +7 at level 16, then entering Epic levels with +9. Most characters would spend their feats for other features, but these superhuman Abilities would become possible.
Superhero Abilities make sense anyway for levels 9-12, 13-16, and 17-20. Since most players today dont reach these tiers anyway, there will be negligible impact. Indeed to emphasize that these tiers are for the superhero genre can entice players to advance onward into these tiers.
Notice where Level 0 might have +3 as the highest Ability. This suggests that the "average" Human is +1. Then below average is +0, and above average is +2. Most Humans will be +1, with at least one Ability at +0, and +2 at one Ability that the individual tends to be good at. There can be outliers, such as +3 for a rare high Ability, or a negative bonus as a rare difficulty.
The monster Attack bonuses add together Proficiency and Ability. Very high Abilities become available sooner than expected relative to the Proficiency. The monsters rarely include magic items as part of this Attack bonus. But the very high number sometimes implies magic. For example, an Attack bonus of +11 at Challenge Level 13, might represent the +5 Proficiency, then only a +4 Ability and by implication a +2 weapon. Every monster statblock is its own concept, but the Proficiency is always true, and it is the Ability and magic that depend on concept.
The high Attack bonuses correlate very high Ability bonuses that can boost AC as well. These big numbers deviate from the goal of "bounded accuracy". Once modifications are adding +11 to a d20, creatures are becoming unreachable by lower tier creatures.
I am ok with the defacto slackening of bounded accuracy that has already happened. It still is at a slower pace than 3e. At the same time, each four-level tier
feels different from the tiers before and after. Each tier is a different league of play. At level 9 with its tier 9 thru 12, the superhero genre is starting to happen with figures like Batman and Legolas. Meanwhile the standard superhero is tier 13 thru 16 and should feel different again. The most powerful superheroes like Storm and Superman are different yet again at the tier of 17 thru 20. The Epic levels truly feel
beyond.
D&D 5e has already evolved its bounded accuracy this way. It is what it is. The big numbers exist. But I also think, these 5e numbers are optimally where they should be.
By extension, a player character should be able to use the feat at level 12 to boost an Ability to +6.