If you have an idea of a spec you want to sim with, but are considering moving around a couple of points, the StatTalentDPSValue button is useful as it'll tell you how much that final point of each talent is worth. Of course the value will depend on what rotation/priority you use and what gear etc. Trying to find the optimal DPS strategy for a DK is a little bit of an art.
Anyhow the last time I ran it for the DW build I got a display that came out like this. (I was running 2 BI, 5 Necrosis 0 Morbidity and 3 Outbreak)
Average for OriginalSpec | 11680
Value for ImprovedIcyTouch | 9
Value for RPM | 5.5
Value for BlackIce | 77
Value for NervesofColdSteel | 150.67
Value for IcyTalons | 158
Value for EndlessWinter | 145.5
Value for ViciousStrikes | 99.5
Value for Virulence | 26
Value for Epidemic | 47
Value for RavenousDead | 209.67
Value for Outbreak | 90.67
Value for Necrosis | 129.6
Value for BloodCakedBlade | 161
Value for NightoftheDead | 0
Value for UnholyBlight | 118
Value for Impurity | 105.2
Value for Dirge | 108
Value for MasterOfGhouls | 880
Value for Desolation | 86.6
Value for CryptFever | 0
Value for BoneShield | 172
Value for WanderingPlague | 116
Value for EbonPlaguebringer | 72.67
Value for ScourgeStrike | 0
Value for RageofRivendare | 141.2
Value for SummonGargoyle | 453
Morbidity doesn't appear in the list because it wasn't in the build. Sometimes you have to put in speculative talents (for instance if you were thinking about dipping into subversion (not usually worth it for a sub frost build)). However morbidity is a special case as it's pretty much equivalent to 1/2 the unholy blight value for single target, so I don't usually put it in. (In this case morbidity is worth around 60 DPS, so not worth it for a straight single-target build)
Now obviously you can't necessarily remove all the weak talents.
I originally did have 3 points in Black Ice, but as you can see it's value is less than that of Necrosis (or of Outbreak which is where I moved it to as I already had full Necrosis), (Necrosis is quite a bit stronger for DW than 2H).
If we want Morbidity we have a few options. Taking points from Epidemic conceivably makes sense in a single target environment however we usually want Morbidity for better AE in which case we want longer diseases, so we'll skip that.
We can't take anymore points from the frost tree (all the talents are either valuable deep talents or required in order to get said deep talents). So it has to come from the Unholy tree. The only real options are desolation (which is useful for AE) and Outbreak (which would get weaker with AE).
Some talents are pretty sensitive to the conditions of your simulation because they'll chance the sequence of actions. Dirge is one example as it provides extra RP and the amount of RP you can use depends on how many free GCDs and may affect the sequence of events. Reaping is a more severe case. So you have to be a bit careful evaluating them.