Subclassing neccessitates a new approach to balancing

Zodiarkslayer

TLDR: A 5 (ish) step solution to balancing ESO class skill lines, instead of classes:

The first order of business is to define global principles that set the cornerstones of how the abilities and passives are structured. Note that I do not mean how high the damage goes any thing that specific. Nobody wants a game where everything becomes homogenised (I can already read the comments: You want to make everything the same! - No. I don't).
What I mean is something a little bit more general. Hence I am calling it a priciple, not a rule. For example: "Self buffs must not be attached to damaging skills.", "A buffing effect needs to be in a skill line appropiate to its function." (i.e. Major Resolve in a tanking line, Major Sorcery in a DPS line, etc.), or "A skill can only combine two effects, not more. (Skills like Chanelled Focus, Cephalliarch's Flail or Recuperative Treatise have too many effects build in and are therefore always a comparatively better option)". Important would be: "Class mechanics must be completely usuable and leverageable within a single class line." (especially corpse creation should be reevaluated with its functionality in Bone Tyrant and Living Death).

Now we can get to work:
Step 1: Divide all 21 Class skill lines into three categories with 7 classes each. DPS, Healing/ Utility and Tanking/ PvP, for example.
Step 2: Define active skills for these types of skill lines and how high their base damage is supposed to be. For example: DPS line has at least: One spammable, one ground DoT, one sticky DoT.
Step 3: Define passives for the skill lines and how high these are supposed to be. For example, DPS: One damage passives with either WD/SD or MaxStam/MaxMag, one damage passive with either Crit Chance, Crit Damage or Ultimate, one sustain passive and one skill line specific buff that scales with the amount of abilities of that skill line used.
Step 4: Reshuffle all abilities of one class to adhere to the above mentioned rules set. Drop skills and passives that do NOT fit the rule set.
Step 5: Fill up the remaining blank spots with new passives and abilities.

The result is a system of relations between abilities and passives, rather than between classes. In it the relation between certain abiltites are known, quatifieable and can easily be attuned. By leveraging existing relations and applying the global principles will reign in extreme outliers like Assassination and Herald of the Tome, without destroying their uniquness.