I don't have an answer for you but, you drew my interest to where I googled some data. This Link:
http://amath.colorado.edu/computing/...tand_fmts.html provides some useful information that my help you.
Briefly, it discusses various graphic formats and defines a .tiff file above all others and the .eps file as the lowest of them all.
So, this may/may not help you . Just thought you may be interested.
I have never used Illustrator but have use other graphics programs (i.e., Visio, PowerPoint, AutoCAD, et al).
One question though: Have you tried to copy & paste the graphic (group all of it) into Word without defining any graphic file format? I have done that with a Visio graphic and inserted directly into Word without problems. You can still size it to fit the desired area.
Hope this helps. If not...sorry...