Defense Rating

Defense Rating isn't a concern: a bowazon relies mostly on avoidance, minions and Dodge, Evade, and Avoid. A bowazon's defense comes through taking advantage of being a ranged fighter and with good reason: no matter how high, DR can't provide your bowazon with 100% protection (not including blocking or D/A/E) and a monster always has some chance to hit, ranging from 5 to 95%. By the time your bowazon gets to Hell difficulty, if valkyries and decoys don't work, no amount of armor is going to help (as anything that can wax your valkyrie will splatter your bowazon); even with +1,000DR, monsters in Hell difficulty have more than an 50% chance of hitting your bowazon, assuming she's fighting monsters her own level…except that the character screen doesn't take D/A/E into account.

Defense Ratings are useless for any class that doesn't have a skill that raises DR by around 200-300% and even with a Defiance hireling, the worst threats in the game ignore or bypass DR. Also, when your bowazon is running (which she will be doing often), monsters will have 100% chance of hitting her (barring Evade) because DR is set to 0 when running.

The playing style of a bowazon requires a lot of running, retreating, and repositioning. Hypothetically speaking, if you know when and where to retreat and when and where to attack, your bowazon won't need DR at all, and if you really need defense, invest in D/A/E.

Physical Resistance

Physical resistance (pDR) is different from DR: while DR reduces the chance of being struck, it doesn't reduce damage. [Physical] Damage Reduced by XX% items are the exact opposite: they reduce physical damage, but don't reduce the chance of being struck. Physical resist items reduce physical damage by its listed percentage: for example, a bowazon with 65% pDR has an effective 50% pDR (as of v1.10, physical resistance from items is capped at 50%), meaning that if an attack causes 100 physical damage, the pDR reduces that by 50%, resulting in 50 damage. This is important to melee fighters who constantly take damage, but for the bowazon, whose defense comes from avoidance, pDR isn't as much of a priority.

Where can I get Physical Resistance (for less than 100 strength)?

Equipment:

Harlequin's Crest shako: 10% pDR.

Rockfleece field plate armor: 10% pDR.

Rockstopper sallet: 10% pDR.

Shaftstop mesh armor: 30% pDR.

String of Ears demonhide sash: 10-15% pDR.

Vampire Gaze grim helm: 15-20% pDR.

Sockets:

Ber rune: 8% pDR when socketed in helms and armor.

Note that few pDR items offer elemental resistance. While pDR is capped at 50%, this does reduce the effectiveness of the Amplify Damage and Decripify curses, so if the bowazon with 65% pDR is hit with Amplify Damage (which reduces pDR by 100%), then the pDR would reduce the curse's effectiveness by 65%, meaning that any physical damage is now increased by 35%. (Not good, but better than taking guaranteed double damage.)

You use this stuff when you know you're going to get hit. The beauty of the bow is that you're not going to get hit, so if you really, really need this stuff as anything but a contingency, then you've already failed.