Why are you taking things out of context? I never said it was useless, what Im saying is that its on the level of Sigliyph. Sigliyph is a pretty decent card, its not bad, but its not amazing either. Once your opponent knows you have it, you change the way you play around it. We have Pokemon Catcher, all you have to do is get out the Klinglang and knock it out.
Plus the deck is very slow. It doesnt have any quick ways of busting out energy, meaning that you need to draw incredibly well to do anything. The deck cant capitalize off Junipers and N's that well. You can only drop 1 energy per turn, you need time to get out Klinglang, the rest of the evolution line is very weak. Anyone thats a decent player doesnt stack their decks with just EX's, you play a few non EX's for things like that and Sigliyph. If I see your playing Klinglang, Ill charge up a non EX and proceed to knock you out, your deck will be too slow to counter attack for the most part unless you draw very well and can stall me out or I could get out an early EX and just kill your line off before you get out Klinglang.
And yes Cobalion discards a Special Energy, but what of it? Darkrai and Blastoise decks dont rely on DCE, my HoOh deck doesnt rely on DCE, DCE is pretty powerful and can end games but in no way is it game over if your removing it.
Darkrai and Eel decks are still very popular. They arent going away, and theres no reason why they would. Mewtwo EX already destroys Eel decks 1st turn, I dont see how Landorous is any different. Not every match up will you see Landorous.