I'm currently wearing a medium armor set, and dual wielding. But I'm about to give up and try a light armor set with a destruction staff.

Light Armor issues
- Magicka cost reduction and magicka regeneration are both too important. With these passive abilities, magicka based skills are way too attractive. The gap with stamina based skills gets larger and is currently not disputable nor disputed.
- The bonus to spell critical chance and spell penetration provides some sort of all in one advantage compared to any other armor type. Combined to the spell resistance passive ability, the light armor is the perfect armor type for any magicka build. It's just too perfect and the gap with the other armor types is partly at the origin of major imbalances in the game.


Medium Armor issues
- The passive bonuses focus too different goals, resulting in something weird and not attractive.
- The critical chance and attack speed bonuses are great, but they are the only bonuses that are truly interesting for a melee DPS role, and this is not enough.
- Missing: armor penetration bonus and stamina cost reduction, in order to compete with the light armor set.


Heavy Armor issues
- The heavy armor set should have been designed to grant players a rock solid tanking role in Cyrodiil; but it's actually an entire failure for many reasons, the most important reason being the armor soft cap, which is too low.
- Even with a light armor set, a player can reach the armor soft cap; considering the bonuses of the light armor set, why should such a player bother wearing a heavy armor ?
- The heavy armor does not grant a decent bonus against magicka attacks; the light armor is much better in that domain, go figure.
- Juggernaut? Useless as an ability for a tank; it should be replaced or combined with another passive ability.
- Immovable? It's great, but one does not have to wear a heavy armor to use it. So bad...


Conclusion
- The light armor set enforces the gap between the magicka based builds and the stamina based builds.
- The medium armor set should have been designed with the same orientation as the light armor set in order to give melee DPS players a real chance to be equally competitive when using physical weapons.
- The heavy armor set is just a joke and is currently useless in Cyrodiil. It's mainly based on heal bonuses, but with the 50% heal reduction granted by standards a tank cannot decently hold the line with an heavy armor set in the middle of a battle.