If you fire random Ezreal Qs and dont hit a target the timer doesn't show in the item. Although it still procs it. Using Windows 7.
Says critical strikes give 3% max mana return. 
bolts can critical strike but do not give the 3% max mana return.
Case number one, possible bug.
Case number two, probably intended. Otherwise, you could regen INSANE amounts of mana in a very short amount of time.
Essence Reaver triggers on the crit and Runaans triggers on the crit - you're getting Mana for critting, you just aren't getting more Mana for having an additional crit effect. It's a little like asking why shiv crits don't restore extra Mana per unit hit, it's just a little confusing because they do apply on-hit effects.
Manamune sounds like a bug though.
