There are a few trees that seem specifically designed for players to take them and buy down to the Dedication talent and then drop them, specifically Assassin (BH), Gadgeteer (BH), Doctor (Col), and Scoundrel (Smu). Each of these talent trees has a direct path straight down to the Dedication talent filled with 80% or higher abilities that are permanent.
I don't know if this is a design intent or not. Personally I am not a huge fan of this idea, of encouraging people to add and drop trees to min/max their character. Granted that whether or not it is encouraged or designed that way will not stop people from doing it; and I do like that you can be selective and build a completely unique character based on what you like this idea stil irks me a little bit. I think the dedication skill should be at an equal spot on the trees and should have some balance on what abilities you pick up to get there. Running straight down one line and picking up all permanent abilities shouldn't be possible. There does need to be some cost for constantly shuffling specializations around.
Just an observation and my two credits.
It's funny that you mention those trees, because my 5 players each chose those trees as their starting specializations. I don't think they saw anything throw-away about them…and I think, were I to actually play a character one of these days, I would love to play a Doctor or a Scoundrel…or even a Gadgeteer. There seems to be a lot of richness in those particular trees that you mentioned, and I could see myself happily staying put in one of those talent trees for quite a while.
Like Dono said, you're gonna have min-maxers in any system. The real trick is how to discourage the Munchkinism while simultaneously encouraging roleplaying, and I think so far this system has taken good steps toward aiding GMs and players in that endeavor. Certainly there's some tweaks and adjustments to make, and even after the rules are finalized there will be the need for GMs to tailor the game to their specific group, but I personally see very little comparative potential for min-maxing in this system (compared, that is, to most d20 systems I've had the pleasure of playing in).
Furthermore, it'd take a good chunk of XP to actually work your way down the trees in order to get to the Dedication talent. Even if you played once a week, with 10 XP per session you're looking at months of play before you get your first Dedication talent. And then another couple weeks of play to gain enough XP to buy into another specialization. And that's without increasing any skill ranks. You'd have to be a pretty patient min-maxer to keep buying your way towards one Dedication talent after another. And while that is happening, I would think aforementioned min-maxer would get a heavy dose of roleplaying; it might even be enough to cure him of his pointless quest to "win."
I think you are confusing min-maxer and munchkin. A Munchkin believes that he can 'win' a RPG by cheating, using exploitative rules interpretations, and being a nuisance. A munchkin cannot be a role-player because he plays the game to stroke his own ego, his only desire is to benefit himself. However, a min-maxer generally plays the game to see how well he can make a character, this can be related to being a Munchkin but most min-maxers are not Munchkins . A great min-maxer just wants a character who is as effective as possible, he does not desire to hurt others, nor does he want to cheat; in fact he may want an effective character because most heroes are effective at what they do. If someone where to make Luke Skywalker, but make him in a way that was poorly conceived and was not effective, that wouldn't fit the idea of what he was in the movies. However, a min-maxer or optimizer can make Luke in such a way that is true to the character and effective, which is well within the idea of roleplaying.
Also, this is something called the Stormwind Fallacy; this fallacy states that role-playing and roll-playing are mutually exclusive, this is a fallacy for a reason. One of the optimizers I know is a great role-player, in fact he is a professional actor. Which means that you the idea that you can cure min-maxing, and that is a good thing, then that's your opinion, but please do not look down upon us, because, we want to play a fun game just like you. We just have somewhat differences in opinion on what is fun in a game. We can enjoy the same games, we can even have fun together, and my making an effective character should not stop you from having fun.
That's just my 2 cents, and my opinion.