There are some things in game that are rare, some that are amazing and some truly make you stop what you are doing and look for a second to say...WOW, that's amazing.
I'm sure the first few times you seen the Ashes of Alar mount flying around Shatt or Dal you had that feeling. Its truly an amazing mount and well, you don't see very many people in game with them. Its rare and you know when you see on that its special. At least in the context of the game, this mount is a thing of pride.
So on to my point, Blizz has announced that they will be releasing a version of this mount via the guild rep vendor. Yes you will need the reputation, and gold to do this but did they have to do that with this specific mount? I mean, this is a one of a kind mount in game, and doing a bit of research there is some meaning behind this. It seems that a young man that was pretty sick, used his Make-A-Wish, wish to visit the good folks at Blizz. He wanted to meet the team that put this game together that meant so much to him. Blizz does do special things in game for people all the time.
Dark Phoenix mount now, will have a different skin and name but the look is the same and well, to me it detracts from the specialness of Ashes. You only need to do some dailies and stay in your guild to get this as the guild mount.
To be honest I'm not a huge mount guy. I do have the Ironbound proto drake from Ulduar 10 and the 50 mount achievement. I never went to Blizz's store and purchased the spectral BOA mount either. I feel that maybe a mount should remain special. For the longest time I only had 1 flying mount on my Chasey. I spent hard earned gold to get that mount too. It took me til almost the release of Uluar to get Epic flying. I had the CoT drake in my bank forever.
I guess I feel like an old man sitting on the steps with his pals and complaining about the change that is about to take place and how the good old days were better but, I don't really see how such a symbol is getting a skin change and being sold to those who want to grind, stay with a guild and have gold stocked up.