Doing anything for 10 straight hours is high risk. That being said, grinding may be an even higher risk. You are easily reportable by other players by being in the same areas for so long.
I used grinding profiles to level when MoP hit. It was lower risk then because of questing bugs (WoW bugs, not HB) and so many people in game resorted to grinding to level. There was/is also the issue of needing to grind in order to collect motes & profession patterns.
So it really depends on why you are grinding (to level vs collect crap), server type, server population, afk grinding, etc. as to where in the spectrum of high risk you may fall.