[quote name='Charles.Surge']I think it's a completely fine concession to make for localization cost... I don't know how big party chat was in DQIV, but 8-4.jp said it felt like over 2/3rds of the text in DQVI was due to party chat, so obviously the additional cost there is significant![/QUOTE]
Problem is that it was discovered that the Japanese version actually had a partial English translation within the game itself that wasn't normally accessible. Even had other languages, as it was likely an attempt to make the localized releases comes out quicker (though it took them nearly a year to do so). It wasn't complete, but it was a sign that they were working on it from the beginning, so there's no reason why it should have taken an entire year to release a trimmed version.
As for it being the first main DQ game on the DS, that means nothing considering SE had done full retranslations for Final Fantasy IV and Chrono Trigger on the DS. The main problem is that SE never really bothered with putting too much effort into the series in the US, particularly when it came to the DS releases.
In regards to the length, it seems the party chat text was more than the regular game script.