I can't get that page to load, but an all band doublet will no doubt be ladder line fed, not coax. If you want a coax fed antenna, it will have to be resonant on the bands you want to work or it will not have less than 3:1 swr.
Either a ladder line doublet with a balanced line tuner or a coax fed dipole with fan dipole arrangement or something like the Alpha Delta DXEE which is a trapped dipole.
Regarding height, take a look at this: http://www.qsl.net/aa3rl/ant2.html
What this is saying is that you need to get your antenna up in the air for a dipole of any design to do more than warm the clouds. There is no DX in the clouds.
This is why so many people who cannot get an antenna way up in the air depend on a vertical for DX operations. A good vertical will have a very low angle of radiation and is very good for basic DX work.