As I mentioned before, they start doing that more and more often when you continue to use the same combo constantly. Some enemies use unblockables more often than others (particularly bosses), but none of them use them as often as their normal attacks unless you don't change up your combo routine a little bit.
Countering and mixing up between air combos and ground combos keeps them on their toes - and as has been mentioned before, certain ground combos knock smaller enemies away.
Blindness goes away with the first hit, but stun animations take a lot longer than that to get through, which is (except for their cooldown frames after big attacks) the best time to get in a decent-length combo. Countering takes as long as the one-two hits you like but does quadruple the damage.
If an enemy is small, you can probably roast the lot of them with a holy water, but small enemies don't have unblockable attacks anyway.
If an enemy is medium, they can be stunned by the guillotine and then taken to town. Or taken into the air and taken to town. Or stunned by Direct, Area, Area - or Area, Direct Direct (I like that combo). Yes, sometimes your combo will be interrupted, but there are other combos besides your default that do more DPS in a smaller timeframe, and most medium enemies are stunned by the opening few hits anyway (except for things like Skeleton Knights, they might need a Holy Water).
If the enemy is big, they're slow enough that you're going to murder them with counters and various combos anyway.
This is true of every enemy in the game. The only ones that begin to be problematic are the Greater Lycanthropes, who need a much more intense Counter treatment than the norm.
Again: if they're using unblockables that much, it's because you are using the same combo too often. This is mentioned in-game via a scroll.
