Overview of the Mystic Enchanting Rarity System

Anerythris

In the current state of the mystic enchanting system, the four rarities are redundant and only provide false depth. This ends up being annoying and clunky to the people that stick to Ascension, but more importantly, it offers the illusion of an insurmountable wall to newer players. Yes, there are so many mystic enchants, but the grand majority of them are hopelessly useless. What might be a pretty line in the fancy trailers ends up being a fault of the actual game, rather than a boon.

The unique situation of Ascension has slowly turned base abilities/spells into underwhelming shadows of their blizzlike entities and forced a lot of weight into the Mystic Enchanting system.
Let's take a more detailed look:

Uncommon enchants: small bonuses to one spell/ability, not related to talents, not conditional to any particular stance or the use of an ability.
Rare enchants: small bonuses to one or more spells/abilities, sometimes related to talents, may be conditional.
Epic enchants: gameplay altering bonuses, giving new abilities or modifying existing ones to an extent that vastly affects the viability of a build.
Legendary enchants: gameplay defining bonuses, the current trend is towards massively inflated conditional bonuses that end up, unsurprisingly, hard to balance.

In my opinion, the system is in need of an overhaul. I will focus on suggestions on improving the rarity aspect.

Consolidate the following uncommon RE categories into non-stacking uncommon REs, as following:

Powerful [Spell/Ability]: Increases the spell's damage by 5%. Does not stack.
Critical [Spell/Ability]: Increases the spell's critical strike chance by 5%. Does not stack.
Quick [Spell/Ability]: Reduces the casting time of the spell by 5%. Does not stack.
Steady [Spell]: Reduces the pushback of the spell by 50%. Does not stack.
Taunting [Spell/Ability]: Increases the threat generated by the spell by 100%. Does not stack.
Subtle [Spell/ability]: Decreases the threat generated by the spell by 50%. Does not stack.
Accrual [Spell/Ability]: Increases the damage over time of your spell by 5%. Does not stack.
Focused [Spell/Ability]: Increases the scaling of your spell by 10% (To clarify, a spell like Wrath has a 38,4% spell coefficient, this will increase it to 42,24%). Does not stack.
Brutal [Spell]: Increases the critical strike damage bonus of the spell by 10% (To clarify, with talents, this will cause most spell criticals to deal 205% base damage). Does not stack.

Rare REs should be adjusted to provide meaningful bonuses and the key factor should be conditional bonuses.
A very common complaint about the current system is that it weighs heavily towards the use of one ability and that any other ability can be used only if the legendary enchant affects it in a meaningful way. The rare REs can take some of the burden of conditional power, so LREs can be designed in a more relaxed way. Several examples:

Starlight Wrath: During Lunar Eclipse, your Starfire's damage is increased by 3%. During Solar Eclipse, your Wrath's damage and critical strike chance are increased by 2%.
Way of the Righteous: After casting Holy Fire, your next three Smite casts deal 5% more damage and add one second to your Holy Fire DoT duration. This bonus lasts for 10 seconds. Does not stack.
Total Darkness: Casting Shadowbolt while in Shadowform has a 25% chance to increase your shadow critical strike chance by 3% for the next 8 seconds.

Epic REs have major inconsistency issues when it comes to how they're designed, how much of a bonus they give and their general viability in the current days. It has been brought up before, so I won't press it here. However, I feel that this rarity category is the most prone to shift actual balance and build diversity. As general advice, my suggestion would be that this category is watched and revised the most. Quality over quantity.
Legendary REs, as mentioned before, have become a stranglehold on builds and their viability. Their power needs to be diffused accordingly to rare and epic REs and the imposed combos made more accessible. Let's take several examples and what may be done about their inconsistencies:

Spell Slinger: an older LRE, with a small Arcane damaging proc and a clearcasting effect.
Booming Thunder: an older LRE, with a stacking bonus to Earth Shock, based on Lightning Bolt/Chain Lightning use. Gives potential to burst specific targets and a proper boon to single target potential.
Twilight Paragon: a newer LRE, that provides a stacking general critical strike chance bonus, with an added nuke and burst windows, all built into one package.
Frozen Chaos: a new LRE that provides bonuses to Frostbolt, Chaos Bolt and Conflagrate and several built in conditionals.

Looking at these four, we can see that the design philosophy has shifted towards putting a lot of weight into LREs, to the point of surrealism. I am not suggesting that LREs go back to what Spell Slinger types are, but the balance might be less volatile if LREs could be adjusted by slightly altering a supporting rare or epic RE that is meant for the kit to work, instead of nuking too powerful LREs into oblivion or releasing new poorly tested LREs to aggravate matters further.