I checked some parser I had, and with 1 point (I usually feat it with 1 point only for VoM proc) Blighted Soul hits for around 13 DPS, on single target boss and with Kithai tank gear in defencive (ofc it will vary a lot depending on gear, boss etc., but this is just indicative).
Full feated is +100% damage on it, so around 26 DPS.
It is AoE, so in your situation (2 strawmen in guild city) it should hit for 52 DPS or something like that.
I have just seen that it is 59,64 on your parse, so it's more or less like that (you have better gear than me also, so that probably makes the small difference).
Sustained rage is +15% weapon DPS, mostly single targeted (you can't hit 2 strawmen at same time with combo as far as I remember).
So it's like 18 DPS if you have 1HE with 120 base DPS (ofc this is an incomplete calc, but again it gives an idea).
Also DT is probably one of the "melee" classes which benefits less of +% of weapon damage.
So on multi-target situation is not so surprising that fully feated Blighted Soul allows you to parse more than Sustained Rage.
Maybe on single target fight it would be different, but in general both Sustained Rage or Blighted Soul are not really so important in the overall DT DPS imo.
Blighted Soul anyway weights for 1-2% Max on overall damage, and if you parse more with that fully feated (so 2-4%) than Sustained Rage, it says a lot about how much DT benefits of +15% weapon damage...
Still imo it's more worth to spend only 1 point in Blighted Soul just for VoM proc, and Sustained Rage it's just a filler to get Cunning Deflection, and a bit extra DPS if in the build you don't need all the prot or the armor from general.
About the build for Tali tanking, full Desacration works in many situations, as Boesch shown sometime ago with those parsers from Zodiac.
Still I think that for tali tanking is generally more versatile an hybrid build.