Well, see, Stirk, that's not necessarily true.
Offense is usually more powerful than Defense, but in terms of technology and such that's not been the case. When offense is higher than defense in historical terms, casualties are massive and lethality rates high. When defense is more powerful than offense, wars take a long-ass time. Where it's perfect is the balance that eventually emerges, eventually, when it is physically possible, when offense and defense are matched, and skill becomes the overiding factor, rather than stamina(defense>offense) or luck/sheer numbers(offense>defense).
Full plate armor beats just about every weapon short of crossbows, in general terms. Longbows could injure but not deliver fatal wounds, most of the time, only being able to go through chain, as was on the arms of some knights and the like. They would just dent and bounce off breastplates. Crossbows could cut through them like butter. But for melee fighting? You had to be better than your opponent, not just luckier than them. Stilettos could get through visors and stab them in the face, or penetrate joints, but you typically had to wrestle them to the ground first(seriously, most fights to the death between knights ended up with the two wrestling with knives, effectively).
In modern times, offense is far more powerful than defense, though we've been trying desperately to keep up(and to improve our offensive might even further, of course). Nuclear weapons, cruise missiles, railguns? Range is as significant a factor in offense as anything else, and with incredible range, speed, and lethality, the only reason defense even reaches the radar in the contest is the ability of modern medicine to keep one alive.
Long story short: I figure functioning armor should(at least eventually) be able to be made permanent, but with a bit more difficulty than weapons, perhaps. Or it could break? I don't know.