Therein lies the problem. The Republicans haven't focused their attention on her because they have and will continue fighting each other to select a candidate until convention time next summer. Hillary can spend the next year campaigning and attacking the Republicans because she doesn't have to worry about any real challenge within her party. It won't take long before the media turns on the 10-12 Republican prospects and takes the pressure off Clinton.
Unfortunately, this is spot-on accurate. If you'll look over the post-1968 period (well, starting that year actually), if one candidate has no competitive primary and the other does then ALMOST ALWAYS the one who had no primary wins the election. This is because the competitive primary usually leaves the survivor bruised and bloodied and exposed.
1972 - Nixon no primary, McGovern not nominated until Convention
1976 - Carter had primaries but not overly competitive after March, Ford nominated at Convention
1980 - competitive primaries on both sides, GOP settled earlier
1984 - Reagan no primary, Mondale nominated at Convention
1988 - Bush had relatively uncompetitive primary, Dukakis didn't clinch until June 7th with CA and NJ
1992 - Bush had uncompetitive primary (but bloodied by Buchanan), Clinton had slightly more competitive one
1996 - Clinton no primary, Dole a long primary season
2000 - Neither primary overly competitive after New Hampshire
2004 - Bush no primary, Kerry a hard grind at first and then cruised
2008 - both had bruising primary fights
2012 - Obama no primary, Romney the last man standing
The only real "exception to the rule" was Clinton in 1992, and he no doubt benefited from Buchanan exposing that Bush was not overly popular among the Republican base. (He also benefited from some of the most shameless media bias I've ever seen in my life but let's not take away the fact Clinton was probably the best CANDIDATE as far as looking like a guy running for President and knowing what to do - and Bush Sr, while in my view a pretty decent President and guy, was a terrible candidate).
This is part of why Hillary has a solid advantage. And while Obama is certainly too far left for my mind, I've never despised him (he's an empty suit but a likable one). I absolutely loathe Hillary and make no bones about it.