Starting with patch 1.03, Boss and Elite Boss rank enemies cannot be shattered. Lieutenants can still be shattered, albeit with a much lower chance than critters/normals. That chance is difficulty-dependent: from 30% to 5%.
It should be noted that rogues with Coup De Grace talent are unable to shatter opponents in melee combat, as all their attacks against incapacitated targets are turned into backstabs, which, despite dealing critical damage, do not count as actual critical hits; even strikes which should technically guarantee landing a critical hit (e.g. stealth attack, Pinpoint Strike) will not work. Therefore, if you plan on utilizing this spell combination on a rogue, you must either resort to using a ranged weapon (since Coup De Grace doesn't proc on them) or not pick up the Coup De Grace talent at all.