I found several other limitations with axis labels when working with Hyperion Reports and charts. Fortunately, there are work arounds, some better than others.
One issue I found when using charts in Hyperion reports is that if you have more than one dimension on a column or row, both are used in the axis labels on the chart. There is a simple solution for this.
For example, in a rolling monthly report there will likely be both Fiscal Year and Accounting Period on the columns, but for the chart only months should be displayed.
To accommodate this, the solution is to put a custom heading that is blank on each of the Fiscal Year cells within the grid. This will exclude the heading on the axis label in the grid. If both the grid and graph are to be shown and the year still needs to appear within the grid, a custom heading can be used on the Accounting Period. Using text functions in the custom heading, the Fiscal Year and Accounting Period can be referenced in the same heading accomplishing the intended results.
Another issue is that in some instances the last Y axis label is being cut off. To work around this, add a secondary axis. This defaults to 0 at the bottom and 100 at the top, with no other steps in between. Formatting the font on the secondary access to be white or whatever the report background color is hides the secondary axis, but gives the last Y axis label a little more room.
Finally, the last issue I had is with the chart axis label being in whole numbers and not decimals. From all of my research I found that the axis label should follow the formatting of the grid, but it is a known issue that it does not. There were several posts on the forum about a non-Oracle approved solution and to use at your own risk. Since this one wasn't my solution, nor is it Oracle supported, I will simply post the link to the forum post and say it did work. I do however find it amazing the only work around is to adjust the XML.