I think I'd use the set amulet and the rare pants, personally. Unless you really want that 100 vitality set bonus.
IF i found breeches with 60+all res, would switching help? That would be a big chunk of vit.
But, 3% dr on my ammy is pretty good, so i'm not 100% positive.
I'd say breeches with 60+ res all would be a no brainer personally vs the rare pants. While you'd be losing some strength, you'd be gaining quite a bit of effective health through total health, and armor. The resists on the rare pants are the biggest draw to use them.