I, too, am interested on what the advice for this would be. Only difference is, I'm playing a dual-wielding gifted blade, with a high wisdom instead of strength.
I would highly recommend the blade skills Absorbing Blade and Combat Slide for survivability. Flat out ignoring a spell against you, twice since you dual wield, is amazing. Combat Slide gives you more 5-foot steps, which you can never have enough of, and you can use it as an immediate action. Other blade skills are helpful. Dual Imbue, Powerful Strike, and Twin Strike are great. I'd also recommend the feats double slice and two-weapon rend. All will help out with damage output. None of those are crit based, I know. Which is what your original question was about.
One of the best parts about being a gifted blade means I get a manifester level. Which means I get a psicrystal. Which means I can cast Share Pain, which splits up damage between me and another willing target, and Vigor, which gives me 5 temp hit points per power point spent. And the psicrystal gets the shared power ability, which means every spell i cast on myself, also effect it. So, in the end, reduce all damage by half, with a ton of temp hit points to spare.
What I'm actually thinking about doing is going into the Dark Tempest prestige class. I know that both the gifted blade and dark tempest rely on the psychic strike for completely opposite reasons. Gifted blade gives it up completely for the ability to cast spells, and the dark tempest uses it to full powers when scoring a crit. I can take the blade skill powerful strike to gain more so I'm not super far behind if I wasn't originally a gifted blade, and I think the benefits of being able to cast spells besides on crits and having a larger power point pool way outweighs the detriment. However, I still want to know how to optimize my build for hit crit after crit.
TL:DR I want advice too, but using WIS instead of STR
The soulknife is a third party class. As such, this should be in the third party forum.
Flagged for moving.
Just play a Mindblade Magus.
Wow, terrible advice
Just treat the Soulknife as any other TWFer except yoi wont need to pay for the weapon. If you can, check out the Psionics augmented playtest and run it by your GM to give Gifted Blade for free based on the dev commenta. Thatll let you take War Soul, which gives you Thrashing Dragon.
Absorbing blade is not as good as it looks on paper, since you have to have focus for each use. Which is also required for the damage mechanic and typically not available when needed.
As Johnnycat93 says, you need the usual TWF feat line to get the offhand attacks. Otherwise there is only two-weapon rend.
If allowed, take a peek at the Soulknife expansions from Dreamscarred Press. Among the new blade skills are Blade Rush (movement as swift action), Stunning Blade, Telekinetic Edge (ignore DR on one hit), or Vampiric Blade (heals for 1/2 of psychic strike damage).
The Gifted Blade/Dark Tempest route is pretty much a psionic magus. If you go TWF and pick up improved critical you are pretty much set. Getting a higher crit range requires you to pick up the bladeskill Emulate Weapon and choosing something like the scimitar or kukri. The trick will be to get more dice for psychic strike which determine the strength of your manifested powers.
Absorbing may not be as good as it first appears, but I still love it. The decision between ignoring one (two) spells instead of using psychic strike for the high damage abilities is a big one, but in those situations where I'm a low health, playing defensively, I'm glad I have it. Just in case I need it. Which I have, once. Could have probably been alive without it, but better safe then sorry.
Yeah, it pretty much is a magus. The mindblade archetype is so similar they could be twins. The difference is powers vs spells. There's a reason I love psionics. The Vancian spell system, to me at least, is archaic and too simple. The only reason it's still around is tradition. Look at what happened with 4e tried to remove it. The entire D&D community lost their collective g%+%!+ned minds. We literally have Pathfinder because of 4e. More to Pathfinder's creation that just the spell system revamp, but that definitely helped. I digress.
Anyways, as far as improved critical, I personally prefer to just have keen on my weapons. Only takes a +1 enhancement slot and frees up a feat. I'm used to playing a fighter, and I was so spoiled with getting a feat every single level. So I'll take anything other than a feat to accomplish the same goal.