There's always +3 armor and weapons, you just have to find them. It shouldn't matter which room they're in because you can navigate the entire vault without fighting anything if you play it stealthily enough.
Sure, it's random, but the vault is also generated using a bunch of rules to make progression always possible. After playing it several times, I'd say its about as about as random as the troll blacksmith quests. You don't know exactly where the things you need are (items vs ore), but it feels pretty much the same every time.