Ok, a lot of stuff in this post. Firstly the above quote.
The trees differ because they are different classes. It is good design to do this. The role in mind is ranged dps, and George has given you a run down on the overall feel for the class which is what you are after. That is NEVER going to change, it was decided upon during the initial design of the class. Hearing more of what George says about the class would be moot.
Saying the trees are different because they are different classes is pointless. The question is what makes them different. Each performs a ranged dps role differently. And to be more specific sorcs and mercs can heal so the base concept of how a dps merc and sorc will work in both pvp and pve will be significantly different as to the degree each is expected to heal. Which is a question they can ask on their forums.
The overall feel post was before the game was live. Sniper Volley doesn’t work that way described anymore. Roll has created a 20sec instant move to create significant range on any melee. Spotter limits the area a stealth can approach a sniper. Evasion now removes all negative effects including dots. The addition of reflect to jugs as well as higher mobility moves in most classes in 2.0 has cut the effectiveness of legshot and alpha strike. And this is from a pvp perspective alone.
I should also point out the quote is not available on swtor.com or anywhere on the current forums. I had to go to a third party website that recorded and tracked all dev posts from current and previous versions of the forums.
This is a MMORPG classes often fluctuate on what their role is between expansions and significant content changes. Everything has a potential to be changed . Engineering has become a melee dps due to the use of mines. So even the idea that sniper will always be long ranged is inaccurate.
consider it to be a state of the union type speech. where we are, where we are going, how we will get there. You cant discount the usefulness of such a post compared to Sniper = ranged dps (sometimes) that is on the current class description.