No one plays paladin. You still lose if you have to waste your entire Turn 4 to nullify the 7/7. As for Drakonid Crusher (I assume you meant the 6/6 [sometimes 9/9] rather than the 5/6), Dragon Warrior only makes up 3.24% of all decks on ladder and most Dragon Priests don't run it. And if you're talking about wasting a Hex on the 5/6, well, you've already lost. No one plays the 8/8 Arcane Giant except for Maly Druid, which constitutes less than 1% of ladder.
Hex is only a dead card against Pirate Warrior since they run nothing stronger than Frothing Berserker.
Hex is dead against any aggro deck and any Jade deck. Probably the best deck for it is Reno Warlock since Shaman would need to waste two at least cards to get rid of a Mountain Giant on Turn 4. Hexing a Tomb Pillager is bad. Yeah, you deny them the Coin, but you -- again -- suffer a huge tempo loss.
It is the best hard removal in the game due to cheap cost and a lack of buffs in this meta
Have you played ladder at all lately? lol. Flame. Tongue. Totem. Small. Time. Buccaneer.