AxesLabel in Histogram3D unreadable

Some improvement can be achieved by filling in the background of the axess labels and by reducing the number of ticks on z.

AxesLabel -> {Style["Mean Rate (tph)", "Text", Background -> White], 
 Style["Duration (minutes)", "Text", Background -> White], 
 Style["Probability Density", "Text", Background -> White ]}

Ticks -> {Automatic, Automatic, {0, .0004, .0008}}

It's not an elegant solution but if you include ImagePadding and also offset the label with whitespace, this should work:

data = RandomReal[{0, 100}, {100, 2}];
Histogram3D[data, 20, 
"ProbabilityDensity",AxesLabel -> {Style["Mean Rate (tph)", "Text"], 
Style["Duration (minutes)     ", "Text"], 
Style["                Probability Density", "Text"]}, 
ImageSize -> Large, 
PlotLabel -> Style["Concentrator Run Duration and Mean Rate", 18], 
ChartStyle -> TSGblue, ViewPoint -> {Pi, Pi, 2}, 
ImagePadding -> {{40, 150}, {0, 0}}]

Seems very hard to control the position of the labels. But at least it's easy to make the labels more readable.

Histogram3D[data, 20, "ProbabilityDensity",
 AxesLabel -> {Panel@Style["Mean Rate (tph)", "Text"],
   Panel@Style["Duration (minutes)", "Text"],
   Framed[Panel@Style["Probability Density"], 
     FrameMargins -> 25, 
     FrameStyle -> None]},
 PlotLabel -> 
  Panel@Style["Concentrator Run Duration and Mean Rate", 18],
 ChartStyle -> "Pastel",
 ImageSize -> 600,
 ViewPoint -> {Pi, Pi, 2}]