How can I improve these homebrewed Defiler/Preserver mechanics?

Question

I am planning a 5e Dark Sun game, and I wanted to use the following rules for homebrewed preserving and defiling.

Arcane Defiling

When a defiler casts a spell of level 1 or higher, each other living being within (spell-level) squares of the caster takes the following necrotic defiling damage:

Spell-Level	Defiling damage
1	1
2	1d2
3	1d4
4	1d6
5	1d8
6	1d10
7	1d12
8	2d6
9	2d8

When no living creatures are within defiling range, the defiler takes 5 × (spell-level) damage.

When 5 or more living creatures take defiling damage, the attack roll or spell DC is increased by 1d2.

The defiler rules should make defilers hated, and provide a mechanical base for some of Kalak's actions in the fiction. The high HP of 5e characters and the low number of spell slots make me think that the higher damage for high-level spells is appropriate.

Arcane Preservation

A preserver can choose to use his bonus action, action, or his whole move to focus his magic and avoid damage to the environment. This improves the attack roll or save DC by 1.

The preserver always gets a +1 so that the preserver path is not simply mechanically worse than defiling, but it comes at a cost.

I am aware that it generally raises the attack rolls/DC by 1, this is offset by tactical rules that gives a similar boost to weapon attacks, so martials are not disadvantaged. Therefore, I am mainly interested in balance between the two rules, or comparisons that assume a general +1 for martials as well.

A good answer would show how my suggested homebrew rules are mechanically imbalanced and maybe offer a suggestion how I can keep the basic idea, but with more balanced mechanics.

Answer 1

As I see it, there are two concerns with regard to balance: mechanical and psychological.

Mechanically, the Defiler's effect is scaling with level, while the Preserver's is not.

At low levels, it's easy for the Defiler to exploit their side effect - just get into range of the enemy and out of range of your party, and you're getting free bonus damage with no to-hit and no save roll.

By level 5, your Defiler could generate 1d4 of unavoidable damage in an area that's 7x7 squares (assuming your "within (spell-level) squares" is a radius that does not count the origin square).

By level 9, your Defiler is generating 1d8 of unavoidable damage in an area that's 11x11.

By level 18, they're doing 2d8 in a 19x19 area.

The higher-level Defiler is probably going to be hitting their own party, which gives you some amount of balance. But the 18th level Preserver is still trading off a bonus action for a +1 to hit or to the spell DC.

Which brings me to psychological balance. These effects don't "feel" balanced - on the one hand, you have an effect that increases with spell level, both in terms of damage and of area. On the other, you have a linear effect that is unaffected by level. We're conditioned to think that things should be affected by level - much of the game is. When we see something that is unaffected by level, it suggest that this thing is different in kind from the things which are affected by level. And thus they don't appear to a player to be balanced abilities.