I think the main problem with constitution is armor being so much more useful than health. Most of the time when armor is down you are instantly dead. But what if 20% of all damage bypassed armor? So that every attack deals 80% armor damage and 20% health damage. That'd both make health more useful and cc harder to apply since it'd be harder to break armor.
Hmmm... that might work to make Constitution more appealing.
It would however, make the Hothead talent worse since even just taking only 9-10 damage would lower your health from the maximum even if you had 300+ armor. Not saying that makes your idea a non-starter, just mentioning the fact.
