Wait, I was going to talk about more similarities than just that one, wasn't I? Well, let's see. Warriors in GW play very differently depending on which weapon they use, while still filling more or less the same role on a team. Most abilities are somewhere between at-will and per-encounter, consuming a resource that you start each fight with a certain amount of and regain throughout the fight at a modest rate. There are support classes that have tactically interesting and highly active roles in combat. Spellcasters can use their wands and staves to zap enemies without spending any resources. Encounters (non-PVP ones) often use multiple types of enemies that work together in interesting ways. Many fights are set up with significant terrain features and things to do besides just hacking away at the enemy.
It's mainly the roles stuff that makes me think of Guild Wars; the rest is mostly superficial, I think. GW does a good job of having a variety of classes performing different but useful roles on a team, each interesting to play in its own way, without any one being strictly necessary. D&D could do worse than to take some ideas from that.