As I read this I was thinking an alternative to removing spell tiers would just be to simply incorporate them all into a single action.
ie. If you have Fire equipped you have access to fire 1, 2, and Flare (they could take it a step further and add the elemental DoT too). Imagine clicking fire on your action bar and a little drop-down menu of spells comes up with the different tiers (defaulting to the one used last). Or if people prefer not to go through the extra clicks just make a macro for the specific spell.
Elemental spells are already an action point hog so combining multiple spells to one action would help alleviate that while also keeping the versatility of multiple tiers.
XI Wiki


