The time delay is all due to language/market. I'm British, but am living in Germany as part of my university studies. Here, they've published up to volume 27, and volume 28 is due out next month.
Maybe it takes so long to get in English because Dark Horse need to print more copies. Apart from Germany, Austria, and parts of Switzerland & Belgium, German as a language isn't used that much internationally. For the English market, they need to produce enough for EVERY English-speaking nation, and also for countries where it's used more than the native language (Scandinavia, Iceland, etc.)
Maybe things would go quicker if a 3-party translation was sorted out. If Miura gave permission to a German publisher to translate, DH could ask to translate the German edition: unless the text ends up too far from the original Japanese, it's a feasible idea (at least to me :-\ )