It sounds to me like you have air restricted so much that you are having to draw really hard on the atomizer to get it to vape at all. It's a balancing act, getting an atomizer to work right. You have to balance air, juice, and heat. Your hard draw is pulling too much juice into the atty, and 10W is not enough heat to vaporize it.
Also, most folks around here are used to restricted DL or airy DL, so 5 ml of juice doesn't sound like a lot to them. However, it takes some time to go through 5 ml at 10W. So the problem you are describing may not be as abnormal as you think.
If your atomizer will allow it, I would slightly increase the amount of air coming through the atty, and increase your wattage to about 15-18, and take a wrap or two off that coil to get it closer to 1.2 or even 1 ohm. I think it will work better for you if you do those things.