For some skills like "Frost Armor", the timer is displayed with an icon of applied buffs and the remainder the buff will last. However, for other skills like "Enchant" or "Familiar" which also last for a period of time, the icon is not displayed.

It may make sense for "Familiar" since there's a visual queue when it's gone, but there's no way to see how much longer it'll last.

For Enchant, when your weapon already has attributes that make it glow, the visual queue is obscured making it difficult to tell whether or not enchant is even applied unless you look at your DPS or just recast it periodically to be safe.

There may be other skills where it is not displayed as well, but these were the two I noticed on the Wizard.