Arena RPTs seem to all run exclusively at a much, much earlier hour of the day, at a time which some can't ever attend. The same goes for another combat heavy clan.
The timings to the April 22 - 25th RPT are actually scheduled so they can be more inclusive (not less), allowing Asian and Australian time zones a possible shot at attending. Additionally, this was one of the only dates/times which key players could attend (if we had scheduled it at a different hour, we wouldn't be able to run this at all).
RPTs of this sort have run at very different times in the past, one was even held exclusicely during very off peak hours. Don't be surprised if the next one is held at a vastly different hour of the day. For now, these are the times we're going with. It doesnt suit everyone's schedule, but no time slot does.