Daemon princes really find their niche as fire magnets of the "damned if you do/dont" variety. If you shoot the
DP, the rhino's full of cult troops make it to your doorstep. If you try to slow the rush of rhino's, the
DP will fly up and start belting your face.
Will a
MoN help vs Tau?
MoN is best against small arms fire, and tau small arms fire is str5 with a pulse rifle (
IIRC), stronger than other races small arms. So a normal
DP is wounded on 4+, and a nurgle
DP on a 5+. Realistically though, that
MoN DP is asking for a couple of railguns to the face which will drop him like a sack of

- 2+ to wound, 5++ invul? You'll die quick smart. I'm not familiar with too much other Tau weaponry, but plasma rifles will swat that nurgle
DP down real quick. Of course, if you go with the
MoT, you're asking for a bunch of Fire warriors to pulse rifle your face into the dirt, as your being wounded on a 4+ and your improved invul doesn't count for

It might help you against the plasma/railguns, but lets face it, once your close enough, a rapid firing squad or two of
FW and a couple of the suits with plasmarifles will drop you. Quickly.
The same thing applies to
IG- a
MoN will make you practically invincible vs the guards lasguns and close combat attacks, wounding you on a 6+ with your 3+ armour save. But, if there is one thing the guard are able to do its pack in ridiculous amounts of special and heavy weapons. One plasma vet squad has a good chance of knocking you down. But if you go
MoT, you will have a much higher survival rate vs that plasmavet squad, leman russ tanks, lascannons etc. But they all still wound you generally on a 2+, and a 4++ does not last forever- especially in the such a shower of high
str low
AP weaponry. And guardsmen wound you on a 5+. Watching your
DP die to a powerblob certainly does suck.
My solution? save points, and go with a Spartan prince

Wings, Warptime and thats all she wrote. All you will ever need

get two of them too