Let me explain the Tier system. Now if you played the short lived Tabula Rasa you would have seen a similar system that wasn't very thought out. Lets use an already created class that people would be familiar with, The Hunter.

Now lets say you pick the Hunter for the first 10 or so levels you would be a Hunter. You would have 3-5 spells or abilities to place your talent points. Depending on which abilities you sink your points into it would open up different classes once you reach level 11. Lets say you want to be a ranged player that doesn't care so much about the pet aspect of the Hunter but you like the ranged weapons set. Ok you have placed your 10 talent points into the right abilities and it opens up the next tier at Level 11 for you to become the Marksman. Now you still have a pet but it is not as powerful as the Hunters but your ranged weapon power increases. Now from level 11-20 you have 5 more abilities to sink points into. You place them into the right options again and now you become the Archer. I will add a picture so that you can better get a grasp on this tiered class system. Also this gives the player more classes to become and even further customize themselves. As you can see from the image below the further on the right the more focused on ranged damage you are and the further on the left you are more focused on the pet and its abilities. Maybe the Beast Master gets to have 3 pets but doesn't use the high powered rifles that the Archer(Gunner) gets to play with. The Beast Master is probably more focused on buffing his pets helping their damage output wear the Archer doesn't have a pet and he can unload huge amounts of Ranged damage. Also this would push the class system from the base 8 to something like 62.