DRK redesign details explained

[TouchandFeel]

Remember all tanks have shield others abilities and TBN is the Dark Knight's version of Intervention/Cover/Nascent Flash/Heart of Stone. The OT (and possibly even the MT) will like be expected to use these abilities nearly on cooldown to protect others in harder content. As TBN shields equal to 25% the targets max hp; a hit that would break a tank targeted TBN would need to be a lot stronger than an attack that hits a Healer or DpS. Raid wide damage will likely be enough to get those Dark Arts procs if you shield DpS/Healers.

A 100k tank targeted with TBN would need to hit by 31.25k unmitigated damage in 6s for the shield to break.
A 71k DpS/Healer targeted with TBN would need to take 17.75 damage in 6s for the shield to break.

A normal Raid wide is likely to break a DpS/Healer TBN while it wouldn't break a Tank TBN if both characters have the same ilevel.

As I stated, if you are waiting on and relying on mechanics, like raid-wides, that will hit the dps or healers to break TBN then you are likely not using it as frequently as you should be (~ every 30s) and are not applying it where it provides the most benefit, on the MT.
During raid-wides, the dps and healers tend to be healed up using AoE heals and so throwing a TBN on one of them may result in the shield breaking but it basically nullifies the defensive gains of it since the out-going AoE heals will still revolve around the health of all the other party members, just resulting in the player that got the shield being over-healed. So you gain the benefit of it breaking and the DA proc but lose the defensive gains of the shield, at which point you might as well have just used a raw Flood or Edge instead.

That also doesn't take into account situations where the DRK is the MT or single tank situations like dungeons, which you will be running a lot of whether or not you feel that they "count".
Also, this will likely not be an issue in harder content like ShB savages since the incoming damage in those will probably be high enough that TBN will always break. This is in regards to all the other content, where the majority of players will spend the majority of their time, and a core and foundational ability for DRK potentially not working correctly there when we inevitably out-gear that content.

While what you are proposing would likely work to help guarantee that those TBNs break, it is still a sub-optimal workaround with discernible drawbacks for a problem that should simply not exist.