The paladin is trash? I doth protest (in Ren Faire-speak, apparently).
You're right that Divine Challenge doesn't work as advertised. It's largely inconsequential in play. But the class has a number of good powers (Wrath of the Gods is one of the best in the game), plus two of the best Paragon Paths; Champion of Order and Hospitalier.
And this is before the release of Divine Power.
from what I've seen, the warden powers are some of the best described and powers in the game (including the implementation of that description). They all have an appropriate primal feel, as befits someone who channels the power of nature for the purposes of defending. Very much the martial-type druid.