This a great question, though I doubt that we will arrive at a consensus answer. Different players have different takes on the core element of the game.
One of the
GREAT things about the 3rd Editions DMG 2 was to talk about the different types of people who play RPGs and the different things they primarily want to "take away" from the gaming table. Beyond a simple divide between "Roll Players" and "Role Players" it went on to discuss differences between a "power gamer" (constant improvement of mechanical abilities to excel in combat), a "thinker" (wants to outsmart the opposition and score an easy win) and a "slayer" (wants to look badass while destroying the opposition). Or an "explorer" (want to peel the layers of the onion of the campaign world) and a "thespians" (wants to help guide a great story-line) and a "goof-ball" (who enjoys getting his or her character into narrative trouble ... and out again). Of course by turns almost everyone dips into each of the
player archtypes. Still one is probably dominant. Personally I run towards an explorer most often and I am grateful that there is such a rich sandbox to poke around in.
A player who is an Explorer at heart probably finds it irritating when continuity discrepancies crop up...that undermines the process of exploration and discovery to have facts change. I know I personally grumbled to myself when Sarishian Steel was described as red in a couple of places in the crusade arc (last arc it was green). Guaranteed to have essentially no impact on campaign play. If the discrepancies are not not critical to the story-line a thespian type player might not care. By not care I also mean, may not even notice.
So in a long winded & round about way, what I'm getting at is that different styles of play and players each have different ideas about what "Effectiveness" means. Or optimization. Though really in the end I think it boils down to how much you enjoy the time you spend at the table. Effective characters are fun to play. Effective tables have enough overlapping interests that everyone agrees ... or everyone enjoys the working out of the disagreements and still has a good time.
One last thing I'll note is that not all styles and people mix perfectly. I personally do not especially enjoy gaming with people who are heavily into the "slayer" mind set (which I personally find 1 dimensional) or with some "goof-balls" whose antics reduce or eliminating the choices of other party members. Some people don't especially like power-gamers. Or thespians. Or Thinkers. Maybe some people get bored when explorer types sift for tidbits of information that have nothing to do with the plot at hand.... So find people you like to play with, or embrace not knowing what you're going to encounter when you sit down.
Did I say that was the last thing? <sigh> Sometimes I'm such a liar.
I think its implied that by optimization your are referring to the part of the game that involves rolling dice. In this game there are basically skills and talents (perhaps you can include attributes). There is obviously synergy between your mental concept and your ability to "bring it" with well constructed mechanics. Bringing it means having the right number of ranks to make a skill useful and perhaps the right talents to add extra options (bloodlines, spell casting) or more "boom" (Weapon Mastery, Smite Infidel). If you want to be "combat effective" at something you need 2-4 ranks at start and be able to raise it by an average of 3 skill ranks per tier and maybe some talent support. I would call that
optimized. I call something "invested" if its being raised by 2 ranks per tier. Probably not optimized, but good enough to regularly beat a DC 15 skill check (eventually good enough to beat a DC 20 check). If you are only putting 1 rank per tier I call it "dabbling." A DC: 15 skill check is something you still fail at with some frequency.
How you choose what your character does, is entirely up to you! Putting a package that makes sense thematically as opposed to "this sounds cool" to me makes little difference if you enjoy playing that character. As Josh has noted in another threat its easy to be good at two things. Or okay at several. Its hard to suck at everything
And its impossible to do a lot of things at an optimized level.
OKAY. Finally. A little secret. More often than not, I design my characters around a mini I have or have seen. That's usually where my ideas come from.