On the last ESO live Eric Wrobel did respond to the HA issue, and mentioned to want to treat that in a more general review on all Armor types to get a new balance between LA, MA and HA.

The thought of this post is to apply consistently & symmetrical buffs/debuffs from Armor passives on Penetration & Resist, like in the updated CP tree.
Why ?
Root balacing the Penetration vs Resist from Armor passives will make it IMO easier to balance tweak the remaining Armor passives.

Change the Armor passives so that they contain:

1. LA passives: 5k more Spell Penetration + 5k more Spell Resist
2. MA passives: 5k more Physical Penetration & 5k more Physical Resist
3. HA passives: 5k more Spell Resist & 5k more Physical Resist

The effect of this consistent symmetry is:

1. LA vs LA is a wash like MA vs MA, because the additional Penetration is cancelled by the additional Resist.
2. LA vs MA is ALSO a wash because both benefit equally from the higher damage of their additional Penetration, which is not cancelled by additional Resist.
3. LA or MA vs HA is a wash because the the additional Penetration of LA and MA is cancelled by the additional Resist of HA and HA has no additional Penetration.

So... purely from these Penetration & Resist Armor passives:

1. LA can do additional Penetration Damage, but only against MA.
2. MA can do additional Penetration Damage, but only against LA.
3. HA can never do additional Penetration Damage, but can also never get additional additional Penetration Damage as well.

I think that fits well to a Rock-Paper-Scissors balancing approach that keeps diversity up.

The changes in passives needed:

1. LA gets 2.5k more Spell Resist
2. MA gets 5k more Physical Penetration & Physical Resist instead of 12% more Weapon Damage.
3. HA gets 2.5k more Armor Resist

The rest of the passives can stay the same, or tweaked as needed.

Thoughts, comments are welcome


EDIT:
I kept the HA issue outside of my post above.
Yes... HA certainly needs buffing, now also acknowledged by Eric
but the post here is to get a more transparent footing/root balance for discussing other "normal" balance tweaks