I think it a concentration of Demiurg ships could easily be explained by the discovery of a system with large mineral wealth, or else a territorial threat from an Ork WAAAGH. These events would be dramatic enough to draw together many brotherhoods, I should think.
As for the pure Demiurg fleet...I have always been intrigued by the idea. Heck, I still have that fan-made PDF with the all-Demiurg fleet list on it somewhere around my hard drive, I think. FWIW, I too have always thought of the Bastion as a bit too pricey, but that has only been in the context of including one in a GW Tau fleet; I can't really offer any first-hand experience as I've never actually used one. That being said, I think a 5 pt reduction to allow 4 bastions in 1000 pts is definitely reasonable, especially given the lack of Demiurg escorts to soak up the remaining 235 points from taking 3 at 255.
@Sig: That was some classic trolling, man!
