Here is a quick fix to make the mouseover font much bigger.
1)Copy the default eq2ui_TooltipStyles.xml into your custom ui folder.
2) Find the line that says ---
TextStyle="/Fonts.FontZapf15"
3) Change it to read
TextStyle="/Fonts.FontMorpheus24"
4) or just download this file and put it in your customui folder
BIG TOOLTIP FONT
another font is
FontKabosGyula30 i just noticed it havent tried it ingame to see what it looks like though. Hope that helps a little.