Having re-organized my much ignored Chaos hordes,
I have discovered something else in Favour of Blight Thralls
(although it is fairly self-evident, in reflection):
Visually; Blight Thralls fullfill the same function
as the original sprue's Chaos Beasts dedicated to the other three Powers
(eg: Khorne Juggers, Slaaneshi Steed riders, and Tzeentchian Disc Riders).
fielded en masse, Gnurgle is no longer 'the ignored Power'...
Although it does tend down the path of  'Army Homogenization'
(ie every army having every type of unit, losing 'character')
the addition of this unit absolutely Does
increase GNurgles visual appeal on the Tabletop.
No, I don't have photos yet,
but I did run the Numbers:
I'm currently fielding
100 Juggernaught Riders, 70 Fiend Riders, 50 Discriders, and (soon!) 30 Thralls.
I quite like the proportions,
and I do feel the addition of this unit adds some needed Balance
to the Chaos Forces;
Visually at  least (GamePlay to be determined).
Now; I do have some question as to whether or no Blight Thralls
should be allowed to move as fast as I have proposed initially,
as Gnurgle is traditionally a slower moving force, akin to squats:
Anyone have any thoughts on the subject...?
As a complete aside;
I have been playing with alternate nomenclature;
as I feelthe name "Blight Thrall"is less than prosaic...
How' bout  'Blight _FLIES_",or 'Carrion Flies' or 'Cluster Flies' ( of Gnurgle') ...?
http://tinyurl.com/y8lw9fahttp://tinyurl.com/y9jc9ew(hehee...clusterflies..."that sure is a clusterfly situation"...)
the swarm/CC/imagery is communicated in Epic Scale quite well,IMO...
On the Tabletop,
I can picture a swarm of them descending on a target
(perhaps a Wounded Titan)
and picking it "clean", spawning a new Swarm...but that's a new mechanic...
{edited: fixed broken links}