There was a time that blends were all that were available to the market outside of Scotland. Since product consistency, low cost and mild flavor were seen as paramount, only blends fit the bill. Glenfiddich, followed by other Single Malt brands, broke this pattern by showing that there was a market for Single Malts outside of Scotland. They can call it a Single Malt because there is no grain and it all comes from the same distillary. It strives to achieve blend-like consistency with the blending techniques.
Blends come in an infinite variety.
I find I don't like the blends with grain. If no more information is given, a blend is probably made up of 3 year old malts and grains. It seems to be a very high-end blend created primarily for the upscale Asian market. I think it'll be there for a while. For anyone interested, this would be the ultimate blend.