<sigh> All right. Since at least this is discussion rather then opinion based refutation I'll stick around a bit longer.
Honestly, the easiest solution is just to make sure no one stacks soak. The game is functional so long as the soak values aren't taken to extremes. Part of the problem is that its just very easy to recognize the strength Brawn/Soak has, and it can be a bit jarring to ask your players not to "optimize" their combat character for…combat.
As concerns Armor and Pierce respectively, I do think the game would benefit from higher armor values. It has always struck me as problematic in a modern or futuristic setting that a human's "stamina" was a more important factor then their equipment when resisting damage. And it does set an odd precedent within this system as well.
By upping Armor and changing pierce to work exclusively against Armor, you have a clear progression in damage resistance, and a clear counter to that progression. Exact values would depend on weaponry, mods and perhaps even talents (the Bounty Hunter armor talents for example would work great "as is" within this sort of system). The Enduring talents and especially Brawn would need to be reworked though. On the whole, armor values should be at least comparable to the soak gain from Brawn/Talents.
Additionally, I would probably implement some kind of "aimed shot" combat action that let's a player take some setback dice on their attack roll but let's them bypass some of an enemy's armor rating. That way Armor is still the preferred way to ensure survival, but even non-Pierce weaponry has the option to be a threat. The attack would definitely cost strain though, so that its a decision to be made and weighed rather then a given.
First off, the comments about levels and difficulty…are a bit misleading because this is not a system with extensive level differences. There is progression, but the characters don't dramatically jump in power everytime they "level up". Or rather, they don't unless they are stacking soak…in which case their power level dramatically increases everytime they acquire another point of soak…
However, these are not "high level" characters. Any starter character can obtain these values and progress accordingly. They do not trivialize content by being "over leveled", they trivialize content because its possible to do so when Brawn and Soak are optimized.
While it is gratifying to me that you "recognize the potential for this to be a problem" (yeah, sorry for being just a tiny bit sarcastic here), I don't really need you to confirm it for me. I already know its a problem, to the extent that my own players are volunteering to re-roll as the disparity within the group is just too great. They recognize that when a properly optimized Han Solo could take Greedo's blaster shot without flinching the system itself has some exploitable flaws that should be avoided. Most importantly, it is not in keeping with the premise and setting of the game.
Obviously every group is different, so some guy who's whole point is to be the tank might be acceptable to some. In my opinion, its contrary to immersion whenever a player knows…KNOWS…that a weapon cannot threaten him or her. While that's perhaps acceptable in a game like DnD (personally, I don't much care for it in any game), in a game that's supposed to be narrative and immersive it really doesn't belong.