Anaris would know better then I if it was intended that the the western monsters could be reasonably fought, I had assumed they were designed to make any success against them pretty much impossible, just as the glaciers of the other continents can not be forced to melt no matter how big a fire we build.
Perhaps it was intended that no realm could survive them, but it was also said that this could be revisited in the future.
There was a time when the hordes were pretty huge. Though sometimes it was overwhelming and hopeless, it was mostly fun. Now, as long as we have our safe land to fall back to, it's easier to tweak things so that it's difficult, and that sometimes efforts need to be restarted, without it being completely hopeless.
If you look at the Dwilight forums, it's been mentionned a few times by different people that it'd be really "cool" to establish a "monster-fighting colony". When you think about it, that's essentially what all of Dwilight's colonies were, especially in the West, and they attracted a lot of players. If you want to fight other human realms, you can do that just about anywhere. If want to fight against relentless hordes, you've only ever really had Dwilight for that. Until it got all populated... and started to decline. BT had sporadic invasions, which also attracted many players.
We just don't have any of that left. PvE was a big source of fun for many players, and it's completely gone. I do think that Dwilight's monsters should be fine-tuned to be just the right strength: easy enough for a large coalition to take the coastal cities, too hard for any of the realms to hold a non-fortifiable region on their own.
Maybe even set official spawning zones, such as the Corridor of Torment and Volcano Nightscree, which would be the only regions to spawn new monster units (that however travel every turn), and which are impossible to defeat.