Wire, over at www.eqmagetower.com did some parsing about the stacking of spell crit chance effects. Here's a link to his post:
http://www.eqmagetower.com/forums/viewtopic.php?f=24&t=184&p=3080#p3080
Short summary of his conclusions. Spell crit chance modifiers that have a different spellslot stack, additively. The only conflict with us is in slot 5, Intensity vs Glyph of Courage vs Fierce Eye. It's possible to achieve 100% spell crit rate, for a short time at least.
Personally, I was curious about which spell modifiers stacked and how. Hopefully this is helpful information.