Here in Canada .. and most of North America, actually .. wedding editors are paid a flat rate by the job. That's how I've been paid for 20 years and that's how I pay my editors.
The definition of job varies:
A documentary, mostly in-camera with some BG music and a few basic titles is one charge. A full blown, edited to the point you want to vomit, custom titles, lots of effects and filters .. that's another charge. A studio charges their clients different rates for different video styles, so you should be paid accordingly
On top of that, there are different rates for how you, the editor, deliver these different formats:
Sometimes I do all the capturing, all the photo scanning, select the music, dump it all onto an external HD, give it to the editor; he/she does the edit, saves the project file and hands me back the drive.
Other times I want the editor to do the capture, the scans, etc and give me an output on DV tape. Sometimes I want him to do the DVD authoring ... all could be different rates. Client requested changes are included in the price.
Nobody in my market pays editors an hourly rate for wedding work. I've never been paid hourly for it.
You're right, HD is enough extra work to constitute an additional charge .. but this market is big and filled with barracudas ... so if an freelance editor wants to charge me more, I turn that job over to the film students I have shackled to the edit desks.
What it boils down to: Are you being paid a fair market price for your work? Do you have the opportunity to take on more than one client? Are you just an editor, or do you have a proper shooting kit ... really, that's the way to increase your fees .. cut out the studio entirely and go on your own .. of course, now you are dealing directly with brides .. and their mothers.
Darn ... I need a beer