DT with no bleedthrough would be terrible, as it would allow you to easily make yourself totally immune to most forms of damage fairly early on, utterly destroying game balance.
Whats more, DT was it was in NV was also fairly bad, for two reasons
1. When it comes to low level weapons like the 10mm pistol, DT allows you to easily max out the damage negation fairly quickly, and makes getting better armor worthless as you can never drop below that 20% bleedthrough cap. In NV, Enclave power armor was literally only as effective as blocking a 10mm pistol as vault security armor was, which is bad. Fallout 3's % based DR system does not have this problem.
2. When it comes to high damage weapons, like the AMR, getting more armor is also basically pointless, as it can never offer enough to reduce it in any noticeable way. At the absolute maximum HP one can botain in the base game, with perks or chem boosts, Enclave power armor can only let you survive like .6 more of an AMR shot then something like Sierra Madre security armor can. And again, Fallout 3's % based Dr system does not have this problem.
DT doesn't have any sort of logical curve of armor progression, and it makes getting more armor absolutely worthless against 2/3rds of the weapons in the game. DT simply doesn't work, even Sawyer admitted it doesn't work when he gave medium and heavy armors in NV DR in his mod, because without them, they were totally useless as deflecting more damage.
DR on the other hand has a curve, manages to make heavy armor offer far more protection again high level attacks then light armor does, and manages to prevent you from maxing out damage resistance against low level weapons(which most NPCs have) early only, keeping the game balanced longer.
If anything cripples armor, its DT. Ditch it, or only keep it for a few additional points of damage removal after DR is applied.