Honestly the only thing that needs to change with TBN is there needs to be a lower level version(Just reuse shadowskin animation) unlocked before lvl 50 and then it upgrades to TBN at 70.

If they keep the risk vs reward factor for TBN then it needs to do more, whether that is adding mitigation, adding healing or increasing the duration to 10s to allow more time for the skill to break.

We compare TBN to other short mits. TBN provides a shield, that is it. Others have some combo of shield and heal or heal and mitigation or all 3. I dont think the 10s shorter cooldown with risk/reward factor is strong enough to justify it's current strength compared to other tanks.