Slightly OT, but this sounds worryingly like your main backup strategy is the file duplication those services provide.
You are essentially correct, but I don't see the need to copy a Windows image.
The laptop came with a Windows 8 DVD, and I have a purchased boxed Win 8.1 license for my desktop. Alternatively, I can download and use Ubuntu if I'm unable to get Windows to work.
Then there's my wife's laptop. It's an el-cheapo Win 7 abomination, but it will do in a pinch.
I've contracted myself out to a media agency for the past couple of years. Their machine is managed by the IT department. I have no idea whether they back it up, but anything important I copy to a shared Dropbox folder any way, just in case I need to work from home.
My email is managed via Google Apps for Business (or whatever they call it now), which I pay a monthly fee for. The 10TB cloud drive comes as part of that. I also rely on Google Docs and Calc, as it's available on my iPhone, laptop, desktop and any other kind of top I can log into.
Apart from Windows, every other piece of software I use is downloadable.
So I only care about the data, and I generally work directly out of the cloud. If I'm not going to have a reliable Internet connection, I'll copy stuff over to the drive on whatever machine I'm using.
My iPhone provides additional access to Google Drive, Dropbox and 1Password. It even has an app that unzips archives and opens specific files in Textastic, so if really pushed I can do basic coding on my phone. That isn't much fun, but it has been useful on the odd occasion - e.g. changing a typo in an include file while on the train on my way home...so once home I could relax instead of having to remember to make that change.
Basically, I wanted to be able to be able to get up and running again the afternoon following a Zombie apocalypse in which all my computers were zombied to death during the previous night.
Assuming I can get into town to buy (or loot if the apocalypse is successful enough

), I will generally need nothing more than Google Mail, 1Password, Xampp, a browser and PHPStorm to get going. And maybe the Gimp if there are images to chop up.
I figure I'll be ok.