We send feedback and suggestions to Bluehole fairly often. We have contacts there that we e-mail on a daily basis regarding new builds (updates), items, cosmetics, events, and anything else coming to TERA. The Product Manager team also holds a weekly call with Bluehole to discuss the state of the game. Throughout all of that, player feedback is given on our end and we request changes to the game.

After that, it's up to Bluehole whether or not to spend time and resources addressing that feedback. As the developers they ultimately decide what does and doesn't take developer priority. Keep in mind they don't just have business concerns to meet, but feedback from multiple regions to consider as well.

Aside from the content we get from Bluehole in the form of new builds, they have provided us with (and we've even invented some) tools that help En Masse create events, turn features on and off (like festival quests, double XP, bonus loot), and do things unique to our region (like Kyra's Pop-Up Potion Shack, Mongos, BAM invasions, etc...). Unfortunately those things rely on the in-game content available. We'll never be able to make a new BG, dungeon, class, or BAM. We can't change stats or tweak skills. That's all developer stuff that's coded into the game.