I think the point of tenacity on tanks is to encourage them to initiate (and take counter-CC or peel) or take CC for the team.
But this post is too real. Merc Treads are the best boots for tank junglers. Tabi are much less useful in the jungle than in lane, where you're actually going to be taking autoattacks from enemy champions.
A thornmail-esque passive or a version of Gromp's buff, where the damage was dependent on your max health and the duration on your armor/MR seems like a better idea to me. One that applies the debuff to hostile spells as well as autoattacks (so you can apply it to dragon).
I'd also be all for a health/mana regen component, or the 10% health increase to make it scale better than some of the other items.
Red enchant scales with AD (thanks armor pen), blue enchant scales with hitting your spells (thanks extra cdr), purple enchant scales with more attack speed and killing more monsters.
I guess you could argue for the green enchant scaling with enemy level ups (their cc getting longer durations), but if you're basing your scaling on enemy stats, you could argue the red enchant gets worse as the enemy gets more armor on level-up.