I have all three houses for Hearthfire built. Each has a seperate housecarl from the hold and a steward that I recruited.

I'm having problems with the stewards, though.
For the home north of Whiterun, I recruited Beleval as steward. I figured she'd be tough enough, and she was wearing DG armor and weapons. But a giant came to the home and killed her IN ONE HIT.
For Winstad near Solitude, I recruited Nadja Stonearm from the Companions. Three bandits showed up, and she went down in TWO HITS.

I've replaced Beleval with Ingjard of the DG, and Nadja with Uthgerd the Unbroken. I am currently smithing and enchanting weapons and armor for both to make them more durable. Anything else I can do to make sure they aren't completely useless when it comes to defending the home they steward???

Has anyone else run into this problem with their stewards?

Don't bother with armor-companions don't wear the armor you've given them when they become steward. Give them health potions.

Do Followers use health potions? Ive always given them potions *not ones you make* and they never use them at any rate i dont think a health potion will stop a 1hko........

It will work with other enemies though...there's not too much you can do about one-hitters. I think only restore health potions work, I don't check often, but my follower usually goes through them quickly.

I'll be sure to enchant their weapons with a drain vitality/health enchantment, so they strengthen themselves at the expense of their opponents.