I have been playing Tera for the past 3 days...I'm to level 26, and so far it makes me realize that non-stop quest grinding has a way of feeling just as lifeless as regular grinding... There's no occasion to kill mobs never listed on a quest, there's no occasion to stop and look around, no reason to ever return to an old zone, there's nothing but being shuffled from one place to the next like cattle with all your leveling practically being done for you, in a never ending stream that begins to feel mind-numbingly linear. Last time I turned Tera off it was as I sat back and asked myself what the hell I was doing, and wondering was I really enjoying this, or was I just stuck in the loop? Then I had to turn it off when I realized it was just a loop and there was nothing really enjoyable about ANY of it.
I guess this could be dealt with in ARR with epic storylines, plot twists, and humorous or touching sidequests. Some truly innovative quests. Or even the occasional break in which regular grinding must be done for even just 2-3 levels before the quest loop begins again. I want to feel like I'm involved in the game's world and lore, where my level is raised by showing courage and skill...not feel like I'm rolling down an assembly line.
The one thing Tera DID seem to have going for it was small details like the stuff you would occasionally see floating by (seeds, or petals, or leaves), the fact that when you follow a river, it actually GOES somewhere that isn't an invisible wall. The bustling sound of voices and pets in the centers of towns, the epic splashes and sprays of blood as you slice into a mob, the little woodland creatures walking around just for show (some which you could kill for no real reason).
That said, Tera completely misses almost all the broadstrokes. Sure the combat system is kinda cool (though purely-action combat would never really work in ARR), but other than that, the story goes too long without giving you any INTERESTING details, every sidequest plot in each area is identical (kill X amount of mob to thin the herd, kill such and such mob to get 'special item, repeat).
Originally I had gone into the 'quest grind' topic uneducated. I liked quests, more quests sounded like more fun. But now I know that there needs to be moderation, or too much of a good thing becomes an incessant flood of whiny NPCs whose issues I quickly cease to care about.
TL;DR: SE really should be very careful about how they approach this whole 'you'll be able to quest-grind all your classes to 50' thing.