How should tbn get changed/updated?

[SalamanderIX]

TBN has a scaling issue for me mostly. And it feels like every expansion since Stormblood it has lost effectiveness.
Because the Barrier is a % of HP, there is a constantly shifting threshold of if it will get broken for the Darkarts proc or not. So you can get punished for getting better gear. More HP = better barrier, but potentially losing darkarts proc.
The second trouble with TBN is against reoccuring damage, such as autoattacks and poison.
Some poisons or autos will break them in 1-2 hits, but some will break them in 3. Since TBN is 7 seconds- this means you have to be hitting it near tick-perfect if it's 3. If there's a 4 hit threshold, you're out of luck. You shielded them, but again no Darkarts.

I noted the trouble with autoattacks a lot this expansion. Most bosses attack not so frequently for middling damage. Not usually enough to break a TBN. Exception was M5S, while not the heaviest of hitters - attacks frequently. M8SP2 also. Otherwise the entire tier1 I don't recall it being useful much either.

Solutions?
1. Scrap the Darkarts thing entirely and make it a more generic shield that costs no MP. A smaller shield with a little mitigation and a regen on it. I know this loses skill expression - but in the scope of a "wider" Dark Knight rework that could happen, I'd be fine with this if they added different places for skill expression.
2. Make the Darkarts proc a lower % than the Shield. Perhaps it's 50%. whatever % makes sense.