Are you saying that you're able to sustain 1 million dps for as long as even 15 seconds? I'd love to see a WoL report on that, if you have it.
As for the 8 enhancement scenario (and I presume you're referring to a 10 man raid comp?), the best arrangement I can see, would be a Guardian and Prot War tank. Then, you'd have the 6 raid buffs that enhancement cares about. The raid debuffs not covered would be the 4% physical vulnerability, and the 5% increased magic damage. There might be a slight (potential) dps drop, compared to your current raid comp, but with the shorter fight duration, you might see a net dps gain.
---------- Post added 2013-06-20 at 03:37 PM ----------
Use this tool, to help organize the raid comp, as it will help with the raid buffs/debuffs:
http://raidcomp.mmo-champion.com/