Perhaps the best way I've seen to handle PA in FO3/NV came from a FO3 mod called Impervious Power Armor that basically turned Power Armor into FO1&2 armor-the armor had both DR and DT, making it truly difficult to penetrate.
That would be the ideal way to give PA its teeth back, so to speak, because right now it just doesn't cut it. The extra 5-6 points of DT generally aren't worth it when compared with the lost benefits and added drawbacks.
Letting Power Armor support its own weight when equipped would be another ideal way to make it much better (and more lore consistent) than it currently is.
I modded PA in my game in exactly that way, and now it actually feels like you're a 'walking tank'. There is one problem with doing this, though: the order of operations for applying protective layers is DR--->DT, which means that the DR has a somewhat disproportionate effect on how much damage you actually take due to reducing how much damage the DT is applied against. For example: with 40 DT and 30 DR (a fairly reasonable combo for mid-low end PA), a 100DAM attack actually deals 30. Were the order of operations reversed that same attack would deal 42 instead, and for higher values the difference just keeps increasing. That would allow the blocking of most attacks while still leaving the tier 5 and some of the tier 4 weapons as fairly dangerous; under the current system, though, PA is actually a little
too strong against some top-end attacks if DR > 30.
Note that I have also modded out the 'bleed through' factor, which means that all those popguns wielded by some factions are essentially worthless; the high-end weapons do enough damage that the B-T effect is not applied, so they are not affected by that change. In fact, that one alteration alone brings PA much closer to its original form as it filters out a
lot of attacks that can otherwise get you nickel-and-dimed to death.