So what they can make a wand with a 6th level spell with 50 charges, at this level, pre epic spellcasters should be able to easily overcome 6th level spells, and be able to trump the ability of 50 6th level spells in an item. The comparison is mute, because, 7th 8th and 9th spells are so more potent, and will be used more over the lesser spell levels. This merely allows a non caster to utilize the spells at these higher levels (5th and 6th) whereas they couldn't before, giving them a little room to bridge the gap in power between Tier 1/2 classes and tier 3-4 classes. And we're talking about pre epic any ways, balance at that level is all speculative and up to the DM to mitigate.
And then there is the other feat, allowing players to craft wands up to 9th spells at 30th is overpowered? I fail to see how this is remotely possible, now for this arguments sake (and everyone's sanity) we'll assume no Epic spells, is it still to much to have 9th level spells in a wand. Hell no, 30th level PC's will have a myriad of items that grant 9th spells, Epic destinies and a barrage of PRC abilities and capstones. 9th level spells or access to plentiful resources for them do not break a game or a character at such a high level.
At that level of gameplay, even more so than the pre epic levels, the DM is really the deciding factor on what is allowed or what can be done, so again, it's going to be up to the DM to mitigate any and all power derived from the PC's.
Deities and Demigods while a great book for concepts and ideas is a horribly written book. It was also written in 3.0 and seriously lacking in any level of balance, and as Morcleon pointed out before the EPH was written (which has it's own issues).You should note that that it takes Divine Rank 6 to create wands that exceed the normal limits for such items. See Craft Artifact salient ability. While not everyone uses the rules from Deities and Demigods, you should at least take them into consideration or mention this information.
Basically, why I have it in there is to allow this PRC to be useful at higher levels, taking a prestige class shouldn't cripple you at higher levels, because the abilities in it don't allow you to grow in power. It seems only logical to allow the improvement of wands, especially to a class that specializes in making and using them. When you take into consideration that you can make wondrous items that do the same exact thing (within the rules of item creation) for roughly the same cost with no spell cap, it seems only the logical thing to allow.
And it isn't a rod adept, because rods are expensive, this class is designed for 5th level characters to utilize wands even more so and gain an edge with them.