The Predator is
AV 13 in the front, which is pretty solid (though, of course, Lances

). Was the Ravager able to get any shots at the side armor and was there more than one? A single Ravager will Pen like 67% of the time (22% chance to destroy outright). They're purpose built for anti-tank, so a tank will suffer. Unless you can hide the Predator or go first (and pop his Ravager) its going to suffer.
The Dreadnought is just doomed however. Haywire Grenades are terrifying. Its only hope is to keep out of close combat with those Wytches. I'm guessing he's taking a lot of Venoms?
Honestly, I like the list. It may be more about practicing with it than anything else. Dark Eldar are difficult to face in an infantry heavy list like Space Wolves. You already have two Long Fang packs (though I'd want to bump the Heavy Bolters to more Missiles), and 2 Troops is usually plenty at 1000 points (though I'd want Melta/Plasma not Flamers on those; ditch that
WTN on the Rune Priest and make it happen
IMO). So it may just be a problem of bad luck + learning target priority against Dark Eldar.