I would take Improved TWF ASAP, Two Weapon Rend is alright if you have decent Strength, but most of your damage is going to be in sneak attack. so if for some reason you can afford to take that over other feats go for it.
But if you're planning on an Assassin build you might want to look into Ability Focus to make Death Attack worth something.
(also...call me paranoid but as a Rogue I often find Iron Will and Toughness are just lovely to have)
As far as everything else goes the Critical feats are solid. Some say it's not needed for Rogues, but I love 'em, especially if you can get a decent Strength score and make those fancy new Sawtooth you got properly enchanted.
I'm not sure you're going to see much use for Bleeding Critical as it's very high level and you have other ways of dealing bleed much earlier on. (Yes Bleeding Critical is stack-able and amazing, but unless this is a high level game you won't qualify for the feat for a while)
The only thing I'm not sure about is Improved Feint. Usually it isn't tough to get into a flanking position--especially if there's a front-liner (Ranger/Fighter/Paladin) in your party. (Leadership by the way is a great feat for that express purpose--also probably more useful than Two Weapon Rend).
Getting sneak attack via improved feint will allow you these things:
A) to presumably stay in front of the Monster you're fighting.
B) Possibly make them flat footed
C) Grant you one attack.
I think it would be more worthwhile to invest in feats to improve your acrobatics for tumbling, so that you can get behind them.
Or Lunge so you can attack at reach, or even feats to increase your movement speed.
Then again if you really want to feint it isn't the worst idea in the world. Just remember, likely scenario: you get one sneak attack, then it gets a chance to full-attack you.
(also don't forget combat reflexes is a pre-req for it)
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So yeah totally good choices all in all. I'd recommend however swapping out Improved Feint and possibly Two Weapon Rend for more complimentary feats. And grab boots of Speed ASAP. With those you should be getting 5 attacks per round on a full attack. Not too shabby when you crit like crazy.
Just my thoughts!
Oh!...And enjoy those Sawtooth! They are truly a beautiful thing. (Don't listen to anyone who tries to tell you otherwise)
retain some of the flavor for role-playing.
Advice #1: Don't use the words "build" and "flavour" for the same character. ;-P
He currently Dual Wields sabres (Thank you dead Red Mantis Guys!), and has the standard TWF, Weapon Finesse, Double Slice, Exotic WP sabre. I was thinking about taking all of the other TWF feats, but it seems to take up alot of space.
Double Slice seems a bit out of place there: Most rogues probably don't bother with big, bulging muscles, as they go for knowing where to hit rather than hitting hard. That means they usually get no more than 1 point of damage to their off-hand attacks (which they often have fewer of than main hand, anyway). And Two-Weapon Rend doesn't really do that much for such a backstabber, either - especially since you have to wait ages until you can get it at all.
I'd rather use other feats: Weapon Focus (sawtooth sabre), for example, makes you hitting more likely. Dodge, Combat Expertise + Improved Feint are also useful for rogues who want to live longer and have more opportunities to poke people's sensitive bits.
So here is my thinking: Just get Improved TWF, 2 Weapon Rend at the appropriate levels, and take the following instead:Improved Critical
Critical Focus
Bleeding Critical
Improved Feint
Ah, there's the Feint! Improved Two-Weapon Fighting's also good, as it gets you another shot at skewering vital organs.
But the crit feats will all take very long to arrive, and they don't really do that much. Instead of bleeding critical, get the Bleeding Attack rogue trick. Costs you only one rogue trick instead of several feats, works for each sneak attack (unless you want to do other things, but you can start with this and let him suffer while you do other stuff), and is generally better than Bleeding Crit (by the time you can take that feat for 2d6 bleed, you already do 7 points of bleed damage with a sneak attack, and it gets better!)
Edit: Would a double scimitar be better? Less damage, but larger crit range than the sabres? He will use two weapons, just not sure if I want combat heavy, or more of a HOLY WTFOMGBBQ!!! When I crit and start adding up bleed dice and such.
Well, you already invested in the sawtooth sabres, so you'd have to waste another feat (or do some retraining, if the GM allows).
And, as I said above, The critical feats aren't the best choice for rogues, because of the high BAB requirements and because rogues don't really get that much out of crits in the first place. Double weapon damage, woohoo. The money comes from the sneak attack extra dice, which aren't multiplied.
It might be a better idea if you can get the Telling Blow feat, which lets you sneak attack with all crits (it's from Complete Something, or maybe 3.5 PHB2, I forget), but other than that, it's not a big thing for a rogue. So why not stick to what you already have and know. using the mantis blades looks cooler than those weird double weapon thingies, anyway.
Any comments are appreciated, unless they are negative....then you make the kittens cry....I hope you are please with yourselves negative people!
Yeah. I forgot to mention: You suck! ;-P