This is what I use 99.5% of the time now, macro excluded :
Sure there's a gap between 55-100, but it's nothing a little foot zoom can't fix if needed. Haven't found a situation where it was a problem.
You may add the Canon 10-22 or Sigma 10-20 for more width. I have the 10-22, but if I had my time again would go the Sigma for economy since I don't use it that much.
I do have the Canon 100 macro, but again if I had my time again I'd go the Sigma 105.
And I do also have the 70-200 2.8L IS. But find I can do without it and haven't needed it since I got the 100-400. I don't shoot much low light stuff.
If I was starting again from scratch, I'd get a crop camera and just the 17-55 and 100-400, then build up from there when I knew what I wanted.