Reworking Shaman Talent "Toughness" to lean more into a real tanking device

this is basically a version2.0 of a former idea i posted here a few days ago. Ill make is short and simple.

Rework Toughness completely, turning it into "Ancestral Zealot" (working title). it should either be a 3/3 or a 5/5 talent and we can tweak the exact numbers until it feels balanced as a talent option, but the main mechanism is giving lightning bolt high extra threat after blocking so it basically becomes a builder-spender taunt while tanking. it should not be a common way of taunting, just making sure shaman tanking stays a challenge, but utilising shields, making it viable in general for offtanking in raids for example.

for the purpose of demonstration i asume it stays a 5/5 talent for now.

1/5

You gain +1% bonus on stamina. you also gain +4 defense while holding a shield. Blocking an attack successfully with a shield adds a stack of "zeal"(working title, max 1 stacks). your next lightning bolt consumes all available stacks, gaining +20% crit chance, additional threat and taunts the target for 1 second.

....

5/5

You gain +5% bonus on stamina. you also gain +20 defense while holding a shield. Blocking an attack successfully with a shield adds a stack of "zeal"(working title, max 5 stacks). your next lightning bolt consumes all available stacks, gaining +20% crit chance, additional threat and taunts the target for 5 seconds.

the fun part: shaman tank stays "the underdog". it makes use of shields and gives them a specific purpose and reasoning to gear into defense while supporting that path. lightning bolt as a taunt looks clunky at first but demands planing, interacts with maelstrom weapon.

any similiar ideas to help shaman tanking become a little more viable and interesting?