Disclaimer: I'm yet to use drudges.
Stats:
So the Drudges are speed 5 (same as other stuff but no way to improve)
their P+S is 13 (effectively the same as a bane thrall/knight but without the weapon master/reach)
DEF 11 (so easier to hit than banes and they aren't exactly difficult to hit to start with)
ARM 15 (what hits is gonna kill but AOE's are not reliable)
Special stuff:
Eyeless sight: (nice, ignores concealment and such. Unfortunately they don't have pathfinder and Asphyxious2 has no way to give it to them. Saxon Orrik will help but isn't in the theme list)
Tough: (Annoying for your opponent but not something to rely upon especially as they don't stand up automatically compared to the Bane Thralls with
UA)
CMA: (only when the Mind Slaver is still in the unit and thus not when brought back with Gaspy's feat)
All this for a 4/6 unit. Lets compare:
Mechanithralls
First off, McThralls are cheaper 3/5.
Better speed at 6
Better
DEF 12 but worse armour at 12 (also bad ue to the fact they have to be within 6 inches of the leader so AOE's are a greater threat)
P+S 11 (nothing great but then you read the back of the card and you can get it up to P+s 15 for a single attack)
Lower
MAT as well so less likely to hit
With those points its hard to see why you would take the mechanithralls. Then you add in the necrosurgeon and the unit takes off in a big way. For 2 points you can bring back 3 of the killed models per turn automatically. This helps a lot in attrition battles, plus the necrosurgeon can heal your warcaster if needed. Plus you can add Brute Thralls to the unit which hit harder and block tramples with their medium bases.
Bane Knights
So they are an elite unit with a cost of 6/10. Soulhunters are cheaper than Bane Knights when in a max unit.
SPD 5 (but boostable by Tartarus)
MAT 6 (but boostable by Tartarus)
ARM 16 (not a bad stat, AOE's are right out for damaging these guys)
P+S 11 (but weapon masters so they get an additional dice automatically)
Reach: This can be a killer for your target. You can get so many more models around a model with reach, especially if it's a medium or larger base as small based models don't block
LOS to them
And what I like most about the Bane Knights, Vengeance. Punish the enemy for killing your models. It rocks and makes the Knights even faster.
Basically the Drudges look good but are expensive when compared to what a unit of mechanithralls can give you and not as useful when you look at a better unit. That's why you'll rarely see them on the battlefield/in other people's lists.
But I'm sure there is a use for them. Experiment and you can find a niche I'm sure.
How about you try out this list:
Lich Lord Asphyious
- Deathripper/Nightwretch (your choice)
- Helldiver
Bane Knights (max)
Cephalyx slaver & Drudges (min)
You're still in a tier list so the Drudges gain
AD to get them in there faster. The arc node can help replace casuties in the Bane Knight unit via Excarnate and punish grouping of infantry models with Death Knell. The helldiver is there to burrow and get to the target. Then slam it down so your other models will hit automatically in melee.