I should note that the chart adds up to 102 senate seats. No, I didn't throw in two extra for some imaginary state. There are seats in Hawaii and South Carolina that'll be up in both 2014 and 2016.
Any Republican should take it as an enormous positive that there are 46 seats that are R+6 or better. Granted, the GOP only holds 35 of these. On the other hand, there are only 22 D+6 or better seats, with the Democrats holding 21 of them.
2012 - We can see how bad this cycle really was. The Republican party really only won 7 of 12 seats where Mitt Romney won decisively. Eventually this should even out if the GOP stops shooting itself in the foot.
2014 - This shows how good the landscape is. Republicans have only one seat in a state that's worse than R+6 and that seat, Maine, is safe unless Susan Collins retires. The four other seats which could be vulnerable are all in the south, Mississippi, Georgia, South Carolina, and South Carolina. Democrats haven't won as a non-incumbent in any since 1996.
On the other hand, there are six states, South Dakota, Alaska, West Virginia, Arkansas, Louisiana, and Montana which should be easy for Republicans. Of course, they likely won't be and the GOP is good at shooting itself in the foot.
There are also six other seats in the toss-up range that the GOP took last mid-term.
2016 - Where the 2012 class should've been good for the GOP and the 2014 class should be, this one is regarded as troubling. Yes, Republicans hold more vulnerable seats, but only one is in a state that should definitely be a Republican loss. It'll be an interesting challenge.