I think everyone on the forum is in agreement that it isn't the horde mechanic per se, but the ahistorical outcomes that result without player intervention. I find it annoying that I am playing as GB, Portugal, Holland, etc. and look to the east around 1500 and see a giant Austria/Bohemia/Lithuania/Castille in 9/10 games. I am of the opinion that regions that a player is not involved in should develop along somewhat historic lines. While it doesn't have to be Muscovy, I would like to see some Russian/Orthodox country control that region. Similarly, the OE was such an important player in the scope of EU3, it can't be WAD that the OE gets crushed in 75% of games that have a start date of before 1600.
Since I posted on this topic a few weeks ago, I have started each game by loading as the Timurids and the GH and disbanded armies and declared war on other hordes to lower stability. I then load up as Holland or whatever HRE OPM I feel like playing and go from there. In most instances, this leads to the Russian countries quickly taking land from the GH and the Timurids getting checked enough that they stick around but don't turn into a super-blob. I was criticized for the "gamey-ness" of this strategy, but I don't see it as a problem as I (as Holland) have nothing to fear from the hordes but only want to see a more historical eastern Europe.
Members of the forum have posted great ideas about how the hordes can be fixed. For example, I think using cores and tweaking mechanics to favor core-province colonization would be a great way to handle this issue.
I think that the ideas behind DW are fantastic; EU has always been too Western European focused. The issue that 90% of forum members have is that two of the largest "additions" to the game (Japan and hordes) were fundamentaly broken when we purchased the game.