Although putting some points into unarmed skill is tempting, I would recommend to stick to dodge. Unarmed FRR without high evasion would not survive many situations and getting 20 evasion at 30 skill level is not enough nor fast enough for me.
Unarmed Combat gives huge bonuses to Dexterity (up to +10 by 42 ranks), meaning that not only does it give you a ton of Evasion, it boosts your Fire/Shock resistance through the roof as well. You also get a lot of hit points from Unarmed Combat at pretty regular intervals.
Compare the first 30 points in each:
Dodge gives the following totals: Evasion +10, Health +30, Resist Fire +5, Resist Shock +5, Resist Poison +20, Light Armor Proficiency, double evasion bonus from cloaks and clothes.
Unarmed Combat gives the following totals: Evasion +20, Health +30, Dexterity +3 (which means another +6 Evasion, +3 Accuracy, and about +12 Fire/Shock resistance).
If you put another 12 points into each, it develops as follows:
Dodge gets another +10 Evasion, +15 Health and +25 Fire/Shock resistance.
Unarmed Combat gets +7 Strength and +7 Dex, which translates into +14 Evasion and about +30 Fire/Shock resistance.
At 50 ranks, Dodge has picked up +15 Health and +50 Evasion while Unarmed Combat has only gained +10 Health and a special attack. This is the point where Dodge pulls ahead of Unarmed Combat in keeping your Rogue alive, but I would still argue that the offense of an Unarmed Combat master does more to keep your whole party alive than the extra Evasion from master Dodge.
The point I'm making here is that Unarmed Combat is not appreciably worse than Dodge at increasing your survivability, and the increase in offense more than offsets this. You get large health bonuses either way (although Dodge gives you more) and enough Evasion bonuses to dodge pretty much everything (Unarmed Combat gives more evasion until you've got most of the Lurker set). Unarmed Combat gives much larger bonuses to Fire/Shock resistance. Even if the Unarmed Combat fighter can only tank 80% as well through the mid-late game (and I'd say they probably last longer than that), by including a third damage dealing character you've increased your party's offense by half. Dead enemies deal no damage, and a straight Unarmed Combat build is very highly survivable while still contributing to your offense.