If the battery isn't variable voltage, assuming original single coil EVOD, you need a battery with LESS output (lower voltage), or at least I do, to allow long drags and no burning. The 2.2 coils are also the best for it, other than possibly DIY. You can't push it harder, although a larger battery unit will last longer and may be more consistent. The 650 maH can last surprisingly long though and the small size is enjoyable. Having multiple EVODs is another way to go, to spread the load, provide backup and variety.
I found trying to get something with a LITTLE more vapor a frustrating experience. The dual coil Kanger and low end Aspire units I found to have only a small increase of vapor, increased ejuice use and LESS flavor, although a bit "cleaner" and suited to some flavors. The Nautilus is highly reputed but no one warned me about the issues with the others so I haven't tried it yet. It needs a better battery and once you get past the small stick batteries I'm not going to carry them around a lot when I have EVODs for that. I'll probably go straight up to the Subtank when I experiment with better tanks again. Meanwhile I now use a dripper atomizer (RDA) which puts out a lot more vapor even at not that much more power (10-15 W) and is well suited to a constant flavor adventure, which I like since I still find EVODs better for my tobacco flavor collection and prefer complex mixes in the RDA. This is using an iStick 30, lot of people focus on the battery but I focus more on the atomizer as being the more interesting variable.