Blind and Slow right now are really two of the less-useful skills, unfortunately. Both of these skills, in theory, are outright fantastic. Lowering an enemies accuracy is mitigation, and is a great tool to use in early dungouns.
I remember using it on SCH when I had a WAR tank to help them take less damage. Combined with FEatherfoot, it really helped push their mitigation of mobs back when I was still a newbie to the game.
Feint applies a slow effect. This, once more, is an AWESOME effect. The enemy attacks slower, thus doing less damage in their auto attacks, and could become useful on some fights. Unfortunately, Dragoons aren't going to use it because it messes up their rotation AND lowers their DPS. But if it became mechanically sound, I think more people would use it.
The biggest issue, however, is not that these skills in and of themselves are bad per se. I am sure if they were more effective/useful, people would use them.
The issue is, that bosses in a raid scenario are often outright immune to them. Even most bosses in dungouns will be outright immune to these effects.
So you are effectively restricting the effects of such skill and hurting the utility of jobs. Paladins flash doesn't help mitigate, it just holds threat. Dark Knight's using DA + Passenger can't blind the target and lose part of their mitigation (Which, however, is a GREAT skill to use on AoE trash pools.) Dragoons will never even put Feint on their bar because - let's face it, it's a massive waste of TP, DPS, and time to use that skill in the current dynamic.
What I'd love to see:
Mobs that aren't immune to slow, or make it so skills like Feint - when applied to a mob - give a temporary skillspeed buff (minor) to members who hit the boss. Make their cast time longer of some of their skills on some bosses? That'd be awesome. Blind maybe making it so that when a mob hits you it outright does less damage instead of no damage (Missing vital spots.) We can't really dodge in a raid dynamic anyways, so why do we keep seeing skills like this being added to our characters when they're useless?
This is sort of like the Tribind issue. A heavy situational tool that likely won't see a place in your kit by virtue of how underwhealming it is. These are skills that I think were intended to be utility-based, and thus I think they need to have some ACTUAL utility/desire to use them if we're going to keep putting them in our kits. That, or remove the GCD and just give them to us as a free-damage skill.