First about unstacked: in that case, you just should worry for stacking DEX and attack if you need it.
Pillager+1: 27
Plunderer+1: 31
Skulker+1: 33
Imperor wing hairpin+1 with max unity rank: 34
Taeon: 23~33 (with DEX+10) or DEX 23 and wsd 3%
I did some calcs (hidden in spoilers), and concluded that Taeon 3% wsd is better than 10 DEX by a considerable amount, so Taeon 3% wsd should beat even Imperor head+1 thats the highest possible DEX head piece up to date. Add extra 20~25 att to make Taeon pull more a bit ahead over the others non att options against high lv mobs.
wsd 3% is relative if it is better than a dex+10. Relative to amount of DEX you already have in your set. Lets say your total DEX in ws set without the extra 10 DEX from head augment is 300:
A quick math shows:
D10dex = (D+fstr+0,8*(DEX+10))*ftp*pdif
D10dex over Dunaugmented: (D+fstr+0,8*(DEX+10))*ftp*pdif/(D+fstr+0,8*DEX)*ftp*pdif
D10dexover Dunaugmented = 8/(D+fstr+0,8*DEX)+1
Suposing 10 DEX affects the same as 3% wsd => 8/(D+fstr+0,8*DEX) +1 = 1,03
So, 10 DEX = 3% wsd when (D+fstr+0,8*DEX) = 267. If that is higher than 267, whats common, 10 DEX < 3% WSD.
For rudra stacked, crit dmg+ is similar to wsd, and +3% crit dmg/wsd is better thn 10 DEX like previously deduced, so there are just 2 possible contenders:
Pillagers+1: 27 DEX 3% crit dmg
Taeon: 23 DEX 3% wsd
In that case, depend mainly of how much attack will make diference, but given how high lv mobs have stupid high defense (something like 2000+) normally 1 att << 1 DEX, while depending of how much debuffed it is/how much buffed youre 1 att can be irrelevant. For dynamis scenario where you are already attack capped with a rcb, pillagers+1 is better, and I think most of time, just pillager+1 will do the trick.