Sorry for the two posts but this thought struck me as I finished my last post. With infiltration in all missions at the GT, I suppose that infiltrating Death Guard could be pretty good. Check this out and I guess compare this with the mechanized list
Daemon Prince- MoN, speed, armor, aura, manreaper, mutation, frags, strength, infiltrate
LT- MoN, speed, power sword, bp, frags, infiltrate, strength, mutation, nurgle's rot
2x7 Plague Marines- infiltrate, 2 meltas, asp champ w/fist
4x7 Plague Marines- infiltrate, 2 plasma asp champ w/fist
HEAVY SUPPORT
1x7 Havocs- 3 flamers asp w/fist, infiltrate
1x7 Havocs- 3 meltas, asp w/fist, infiltrate
This army has 58 models as opposed to 47 in my last list and would start closer to the enemy. It's biggest weakness is that it is SLOW.