Same problem. Simple fix if like me you just want Safari to operate essentially as it did before.
I've never commented before. Consider my computer skills inferior to an 8 year-old, and was shocked to find my hunch actually worked.
The problem seems to lie in the operating system trying to integrate every aspect of its functionality and content with every type of search conducted in either Safari or Spotlight which is now a jumble at best (I'm back to searching in the finder) and seems to snack on email content.
So, in Safari, open preferences.
Select the Search Icon
From the pulldown I have selected google as my search engine.
I have selected Include Search Engine Suggestions which are often useful and occasionally comical.
Do not select any of the smart search settings.
It seems to send Safari on a wide ranging search of the African Savannah to load a simple webpage because it looks everywhere else first before it loads. If after all that hunting about it thinks it might have the page or a piece of it somewhere local then it gets a headache instead of just looking for it on the web in the first place.
I have no idea what smart search is or why I would want to search spotlight on my browser or the web from spotlight but apparently it's so smart it's "too smart for its own good." Huh, maybe artificial intelligence is already here. Yosemite has a sense of irony.