Some things in the game are really poorly balanced. You can dump 15 points into Firewall, and it's 372 damage/second will barely scratch an enemy in Flames of Vengeance.
On the other end of the scale, 15 points into Splitting Arrow on a Ranger built for Critical hits will do about 50,000 damage spread out to a crowd.
Build a character the way you want to, and you should usually find a way to make it work. If you want to play in melee, then play in melee.
My most recent melee build is an unarmed character focusing on Strength, with points into Vitality and Spirit as spares. The skills she used were Unarmed Expertise, Battle Rage, Thousand Strikes, Whirlwind, Life Leech, and Death Blow.
Whirlwind might not do a lot of extra damage, but it adds your normal damage to the swings as well, and it hits every enemy around. The cooldown goes down with points as well, gong down to 1 second.
Battle Rage is an excellent multiplier for melee damage, Thousand Strikes is usually a one-hit kill on normal enemies, use that as often as you can.
Don't underestimate Life Leech: It is extremely powerful, almost-game-breakingly so. It is an instant restore for a good percentage of your health, and every hit can trigger it. It can make healing almost unneeded in most battles because you'll recover most of your health from fighting normally.
What level are you at when entering a Flying Fortress? You should be at least level 26. Even then, it's extremely dangerous. A level 26 Black Ring is much harder than a level 26 enemy of another type, which is appropriate. The Flying Fortresses are the toughest challenges in the game, and you're rewarded for completing them - enter at level 26 and clear one, and you should gain four levels worth of experience.
