Hi!
I have played various MMO titles many times, but most of these games are already dead. I came across TERA recently and I wonder if the game is relatively alive? Can I find players to play together, active guilds? Generally, is it worth of trying? 
why not to check recent forum post and see the answer?
tl;dr : not worth. dead game. p2w, grind fest. better to try other games
Sure you can find people to play with in Tera and guilds will come if you stay around enough to level up.
However, to answer your question about the game being dead or not, I will tell you that you may not find people for a specific content at any given time. The community runs on its own self made schedules and participation in several contents changes with events. At some point it may feel completely dead while having people around you.
You can give it a try and see if it works for you, the combat system is still one of the best out there so the game itself is enjoyable. Whether your activities of interest match those of the community or not though, is something you'll have to discover.
