A disorienting effect much like a Hunter's Scattershot or a Mage's Dragonbreath, it does not suffer from diminishing returns. All of us have it. But, what can it be used for?
When soloing, it's easy to tab-target an extra mob and hit blind, giving yourself a few seconds to finish off your primary and regroup. When dueling, it's classic for the blind and bandage combo (pallies can bubble and LoH, so stop crying foul when it happens to you). It's great for arena, to stop that caster when your kick is on cooldown. But what about when running dungeons or in a raid. Could you possible use blind as a form of crowd control? I do.
Especially in heroics, this can save a wipe. If you've got a good set of cooldown timers, you can keep a close watch on your sapped target. Use your discretion. If your party is still fighting off two mobs and your sap only has a few seconds left, run to your target and slap a blind on it. That 10 seconds should give your party plenty of time to finish the active targets and reposition. This is one of many seemingly simple things that will not only impress your running mates, but will also make you more valuable than just for raw dps.
Think about this. You are in heroic Botanica and you're working the 5 mob pulls after Thorngrin the Tender. You can't CC the fleshlashers, which seems OK because they aren't elite, right? You can just burn em down no problem? Wrong. Those suckers hit on leather for 1500-2500 NON crit. And they have alot of health. They need to be either off or pet tanked, and they NEED to go down first because they will destroy your healers. So what about the other three Blood Elves? Not only do they do some wicked AOE that your tank needs to move out of, they have awful aggro issues. If you see one running away from your tank and towards a mage or a priest, tab target and slam that blind. So long as no one touches it, problem solved...for the next 10 seconds anyway. A crude example, but hopefully the point is solid.
So, to answer the question, is Blind a viable form of crowd control? Yes and no. It does have a 3 minute cooldown (thanks blizz for that 1 minute cd tease) without talents, so that is definately a limitation. It's nothing like a hunter's chain trap. Can it be resisted? Yes,and generally, if a mob is immune to poisons, it will be immune to blind. But when it does work (which in my experience is 98% of the time), you've effectively stopped that mob in it's tracks for the next 10 seconds. Try it sometime, especially to lengthen the duration of your only true form of crowd control; sap.