Kakashi is kage level shinobi.Whomever says otherwise is ignorant.A kage level fighter, simply means, that you are strong enough to be considered for that position.
And Kakashi can take on Deidara.If it wasn't for his bad aim (due to inexperience with his MS ), he would have gotten rid of Deidara pretty early.
Edit: People overrate Deidara simply because he possesses a strong tech.Well the thing is everybody does.... and if they hit you with their so called "finisher" -you're dead/defeated.Tsunade, orochimaru,third raikage and A could all tank c4.Genjutsu users could take him out pretty quickly,and most high level folks would have taken him out(or restricted his movements), before he could ever perform it .Notice that in all of his fights, Deidara never used c4 in the beginning of his fights, so why would that change?
You don't hear me saying that Hidan is the most dangerous guy in the world, because of the fact that he can take out everybody.You're in trouble, If you don't know about his abilities, and have you seen a lot of fights, where blood is nonexistent ?