Heavy armor doesn't have stamina regen so maybe you meant medium armor?
Light Armor gets caster related buffs like mana cost reduction and improved mana regeneration.
Medium Armor gets Stamina Regen, avoidance, and Crit Damage and Chance.
Heavy Armor gets Health Regen, Extra Armor, and Improved Block.
I was actually able to cap out my Armor Class at low levels without the addition of a shield in all WHITE Heavy Armor while using a 2handed sword. I would assume that medium armor with a shield and the right set up / abilities could come close.
The extra Stamina Regen from medium should help with blocking more, meaning you might be able to tank in medium armor to some degree via the use of your shield.
Properly using block / bash / roll should help mitigate a lot of damage by itself. Throw in a few class abilities that regen life or improve damage reduction / avoidance and you might be able to tank in Medium armor.
I think of it like this: PURE tank = heavy armor + sheild. DECENT tank = heavy armor without a shield. Moderate Tank = Medium with a shield. Poor tank = Medium without a shield. [censored] tank = Light with a shield, totally squishy = light with no shield.
Think of it as a kind of gradient and see where you want to fit in.
On the other hand you can go for overcharging your stats and try to squeeze out as much possible armor as you can and go heavy armor sorcerer with a shield and use your armor buff spells. Dunno how that would work but would be fun to try lol.