STF mod creator, Modcrafters.com admin, CampaignCreations.org staff
Guild Wars has a few fundamental changes to the RPG concept that must be recognized to avoid comparing it to a traditional RPG and be left disappointed. You listed one very important one, armor. Guild Wars was designed first and foremost with PvP in mind. Contrast that with something like WoW, where Battlegrounds was added as an afterthought and balance issues run rampant. As a PvP-centric game, armor and weapons have a "perfect" value. For swords, the maximum damage range is 15-22, with an attack speed of 1.33sec. Instead of ever more powerful weapons, you can customize weapons with a prefix and suffix item. For a sword, those items are a Sword Hilt and Sword Pummel. These customizations also have perfect values, but it is the differences in choices that set players apart rather than hard numbers. You see, the intent of Guild Wars is not who has grinded better gear, but rather who uses the best strategy, and as such the perfect values ensure everyone is on equal footing.
In Singleplayer, you do have to find or earn those weapons and customization items (they are usually salvaged off of other weapons with the enchantment you want). You can use your SP character in PvP, or you can create a PvP-only character. This type of character gives you a menu of all armor, weapons, and customization items. Thus, gear is not intended to make you more powerful, but rather give you more strategic options.
The more expensive armor that do not give additional benefit are known as vanity armor. They simply look cool. You don't have to get it. That's one of the nice things about Guild Wars -- you don't have to look like a bag of skittles. Your look is up to you without worry of sacrificing stats. Some of the vanity armor is very difficult to get, so they act as a status symbol.
You mentioned dyeing, another fun feature. You can not only dye your armor, but also your weapons, shields, foci, even bags if you so choose.
The "stash" as you call it is actually the only way to share items among characters on the same account without a third party. As you become more familiar with the game, you'll probably find a lot of the stuff you've been trying to horde is actually somewhat useless and you'll know what you can sell or trash without worry. After that, you'll find you have plenty of space. Also, each Campaign adds an additional tab to your Xunlai chest. Heh, and if you think you don't have room now, I played back before they had the Crafting Material tab, so literally 70% of my box was taken up by twigs and cloth. =oP
Where Guild Wars can become addicting, at least for me, is in
build creation. There are thousands of skills in the game, and you get to mix two professions of your choice together, lending a lot of creativity to your tactics. The designers fashioned the gameplay similar to card games like Magic: The Gathering, where you choose your deck and strategy beforehand. This is reflected in the game with the limitation to only 8 active abilities and being restricted to changing those abilities only in towns. But, while in a town, you can completely change your build, skills, attributes, everything, and all at no cost. This lends variety and flexibility to your characters. Not to mention you can even change out your secondary profession (for SP characters, this is earned later in the game).