I'm wondering why they're tanking with face with two swords in hand. Their str is 23, so they should be fairly good with parrying I'd think.

Nope. You're a specless dwarf with imperceptibly better parry and less hp, but also giant size and the ability to bash-lock with high unblockable damage.

Even if you had 25 str it'd still suck because 18 dex basically doesn't dodge. Compare with giant ranger pre-wildfam, it's just as bad (but at least you have phys resist).