Are you going Elf? If so, Dex > Con/Str/Int > Wis/Cha. If not, you'll probably want to consider a Strength-based build. If Str-based, 17-tome into Dex, and then Str-max, Con/Int secondary.
Do you have a Dex tome? A build with <11 Ranger won't autogrant Greater TWF, which has a Dex 17 requirement. If you're Dex-max that's no issue, but if you're Str-build it's hard without at least a +2 Dex tome (1750 favor tome?).
Nothing terribly wrong with going Fighter, and /2 Rogue gets you Evasion (and you can get Improved Evasion w/Tempest T5). Bonus feats help a lot! Get all the cool stuff
Tempest Core 4 gives +1 Crit multiplier to both weapons which will hurt to miss, but you can get Kensei Core 3 to make up for half of it at least. Probably go all-in on longswords, given Knight's Training and the higher base damage? You'd also only get to 90% off-hand, even furthering that point (and missing off-hand DS). Probably look more for a debuff dagger and a DPS longsword (perfect with Sentients too).
Sorta makes more sense as a Str-build then though, which allows you to save a bunch from racial (Elf for Displace or go w/e race then?) and you can then grab Power Surge & Opportunity Attack which is pretty nice. 42 Tempest, 25 Kensei, 6 Stalwart? Idk.