I get cold hands, too, below 38 degrees with my dry gloves. There's nothing worse then that 5 to 10 minutes of pain after the dive as they defrost. This year has been the best year for me yet, with only one episode in many dives (flooded glove). Here is what has finally worked for me:
1) Warm core. Make absolutely sure your core is toasty warm. The core warms the blood which goes through the limbs. I spent another $200.00 on undies to go under my undies (layering) and it has worked.
2) Circulation. Make sure that there is no blood flow restriction in the limbs, like too tight wrist seals or thick seams pinching off blood flow.
3) Thicker/better liners. The ones that come with the gloves are fine above 45 degrees, but in the real cold water you need thicker liners. I bought good quality micro-fleece ski glove liners at REI. I had to get a bigger blue glove size to use them, and it sure diminished the dexterity , but it's worth it.
4) Room in the gloves. Not too much, but enough to hold enough gas to insulate your hands. If the gloves are too tight, there's no room for the gas, and the water sucks the heat right out of the hands.
5) A good flow of gas to the gloves. Whether you use a piece of tubing or some material from your wrists, when you lift a hand up while diving, your glove should fill with nice warm gas.
6) Argon. If it's just a placebo and doesn't really work, don't tell my hands that. They believe it and can absolutely feel the difference.
7) Warm hands before the dive. This is a biggie! Cold temps while suiting up can chill the hands before you even get wet, and then you've already lost half the battle. Warm gloves (not the liners) while suiting up is a must. I also take a tub of hot water and soak my gloved hands in the hot water and heat my hands and gloves up as the last prep to the dive. My buddies call it the "hand Jacuzzi".
Seems like a lot of stuff, but once you're dialed in it's really not much effort at all. And this year has been my warmest hands yet. Today's two dives were in 36 degrees and my hands were warm all day!
Good diving!