Cauis Cossades from Morrowind is a skin a addict, and why the locals claim that he handles it better than even the Khajiit, it is still stated that his superiors are worried about his sugar addiction. And yet this is the man that the Nerevarine takes orders from.
Then in Oblivion we see the Blades as the personal guard to the Emperor, yet they fail to complete that task, even when moving through a supposedly secret passage. And then we move through the game to meet Jauffre, an old man. Now, I know that he is a skilled swordsman, and an expert blade(if there is such a thing) but that does not change the fact that he is an aging man. And no matter what skills he has it doesn't not change the fact that the life he has led is coming to a close.
After the oblivion crisis, then came the Great War. Where were the Blades then? 100 of them had been killed, their heads delivered to the Emperor, and the rest were being hunted down and exterminated. Not at all the legendary Dragonguard that they took influence from.
And of course in Skyrim there's the petulant, controlling Delphine, and the old lore master Esbern. Delphine may be a skilled woman, but she is not an effective leader. Her skills with speeches and leading men would fit better in the role of a slave master, as she wishes for complete control over her men. She is not the warrior that the Akaviri men used to be when the Blades originated, she is a spy, without many resources, running from the Justiciars with only an old man as backup. The only truly skilled member of the dying blades is the Dragonborn, and Delphine refuses to deal with him unless he agrees to kill the peaceful dragon Paarthurnax.
So, are the Blades really this special group of skilled soldiers and spies? More of a group who's reputation has protected them all these years. And now they have been hunted near exctinction, if they had the skills they claimed to have, they would have been able to protect themselves, but obviously they are not the skilled soldiers they'd like you to believe.