I have discussed this problem with DW and i have send an Arabic font but i don't have an answer .(search in the old forum)
I think the problem is with the new text engine and not with the font engine because the letters appears in screen correctly but the order from right to left is not respected and text is scrambled.
This is the same problem with some other soft like Macromedia Flash.
I can give you a solution that can help , look at
www.moon15.com for a program called "WASSET" it allow to write in arabic in Flash or Opus Pro 04 with some special fonts given with the program , the fonts must be embeded in the exe or must be present in the user computer.
they do not need an arabic enable windows system.
But i think if DW changes the text engine to accept arabic fonts like in Illuminatus 4 bis to opus xe 2.81 is better.
Hope that helps.