I don't think that is a significant issue. It's only an issue if you aren't very good at judging when and how to use it and against which enemies.

If you've ever done the content before as a Dark Knight, you will have a good idea of what breaks it although you can probably judge this just based on your memory of the incoming damage on other tanks, or by the item level sync. I rarely had an issue with this when maining Dark Knight in Shadowbringers.

If there is an issue to bring up at all, it is merging the damage reduction of Oblation into TBN to reduce bloat, and possibly self-healing (although I wish tanks could be unique, with Dark Knight being the shield tank instead of just being a mix like the others became in EW).