I have no points in Misty Veil (I either dual spec SMN/SCH with all points in SCH abilities, or go all-in for BLM), and don't see it worth adding to its own slot on the bar by itself (controller user so space is at a premium) but I don't want it to go completely waste. So I have a macro for SMN I wrote for 'range attack' I usually use against Bards or BLM's who are at range obviously, and are attacking me. If misty veil is not on cooldown, that's what it uses, if it is on cooldown it immediately jumps down to the next spell in the list in my macro that's also appropriate fore that situation, and if that's on cooldown it uses the next one which has no cooldown other than GCD. No DPS-hindering /waits are programmed into my macro so it will always use one of its three abilities, and if it uses Misty Veil and I want to use the next two I just repeat the button.

That's basically how I deal with letting the ability not go to waste altogether, while still ensuring I'm using it on ranged attackers vs someone right up on me, and letting it share space on my controller with a couple of other abilities so I don't have a dead spot on my crossbar during the cooldown duration.