As it so happens I and my buddy have been duoing the game since we came here back in January, and He's a Whirlwind TWF Khop Kensai, and I'm a Tempest Trapmonky Khop TWF. We've alwasy been within a rank or two of each other. Occasionally I've lvled a day ahead of him, and even in those cases, he's out damaged me by lots. I WAS pretty close when fighting my FEs back in our middle levels, but now at level 17-18, he's back to outclassing me again by lots. With his fighter haste boost, better crits/seeker, and of course all the Kensai, it's just no contest. He's even REALLY slack at gearing. Where I've picked up the Abishai set, Bloodstone, and some specialized beaters, he's been content with his +5 Metalline Khop of Idon'trememberwhat and +4 something Silver Khop of blahblahblah, both of which I IcyBursted for him. I have to swap 4 different robes and 2 hats situationally, 3 different goggs and 4 rings, 2 sets of gloves, all just to be able to pull off the skills a Ranger should naturally be good at. He doesn't even have 2 hotbars. ONE HOTBAR... it makes my head spin.
What I bring to our duo is the ability to pewpew the casters waaaay back behind the fight before he gets in range to engage, buffing us with resists and FoM, locked chests, doors and traps, contributing to DPS and dividing/conquering. All of which he could manage without, or with a hire + pots.
Don't get me wrong, I like my toon and I'll be TRing into another Ranger, but:
There's no doubt in my mind that Fighter TWF > Ranger TWF.