Even in the original games, PA was not a god mode. So long as the enemy has heavy weapons, they'll be able to take down your power armored self quite handily. If they don't, like they're some sort of poorly armed FO3-style raider group for example, then they'll be crushed in much the same way they should be crushed when you show up with a panoply of prewar tech and plasma guns and stuff.
Edit: In the first game, the major threats to power armor were thus: Mutants with energy weapons, deathclaws (who's claws pierced armor and tended to knock you down), and the ocassional guy with a minigun or rocket launcher. With the minigun mainly being a matter of getting enough hits through for the infamous 0 damage instakill.
In the second game, the major threats were, again, guys with energy weapons (esp enclave), guys with gauss weapons (also usually enclave), mutants with energy weapons, and guys with heavy weapons. For much the same reasons. Also deathclaws.
In Tactics, it was pretty much the same, except that by the time you got PA, it was mainly a matter of facing a truckload of killer robots with heavy and/or energy weapons.
I'll take any of these systems over FO3 style "yeah, raiders with BB guns and .32 pistols can kill me in power armor. Oh, and I can kill Enclave shock troops with my trusty police baton. Derp derp."
