I got that perk, and now my DT is always shown with +25, and it seems to apply, even when I'm not dealing with explosives.

I have both ranks of toughness, subdermal armor, reinforced spine and big brained, so I should have a DT of 13 with no armor, instead it shows 38.

And wearing my reinforced Sierra Madre armor and my Atomic-Valence Tri-Radii-Oscilator my DT is well over 60 when it should be around 36.

Not that I'd really complain about being near invicible, but I am.
I just take mag after mag from enemies then just heal up with their blood sausages, the game has no real challenge anymore.