It all depends on the type of game you want to play. I played a watchman girl with 10 STR but 32 DEX, nevermind force jump, dualwielding hyper upgraded sabers with master flurry and master speed and sneak attack, I was curbstomping pretty much anything when my sneak attacks got strong enough. In my experience, Attributes are key to owning everyone, if they are run of the mill all of your attacks will work but if one is leveled up or boosted past the level that baddies can get themselves, then you have yourself a 1-round k.o.
In any case, guns are overrated. You can use them, but you're better off with just the swords. And You'll get much further as a jedi guardian if you upgrade all your melee combat feats and reduce you attack penalties than if you try to balance both. Defensive force powers make it unneccessary to level up your charisma and wisdom, but you still need that crowd control, and more specifically, the AoE damage factor. I had force scream, though it was too weak in the end, and by Onderon I never used it since I could deal the same damage with each saber blow, and I had five saber blows.
And yes. You MUST have master speed.
Oh yeah. You should go with dual wielding, not a double edge sword, because you get double the upgrading slots