Last i checked, Tainted Areas are not dependant on the Seed, they are just randomly chosen during the creation of the world, so you could load the same seed twice and the taint area would be in one but not in another... (Could be the same with stuff spawed during creation like obelisk, crystals and the like.)
At least that was in the version released after 1.2.5 dunno if azanor changed that.
If you need tainted Areas, then you should just make them more common, in the config.
Hmmm... Alright, just tested it and never mind. You're right, the desert had no taint.
I guess I've been so used to things being seed dependent that I immediately assumed. *sigh*
One can bother to use a See-based random or just the default, time-based on. Whilst ore generation is usually former one (given the method gives you a random by itself), any other things in IC are latter as well. Not suprised to see something additional like V/T is done with a random random, as well 
A releated Question: Is anyone encountering a mysteriously disappearing of already tainted Areas with Mystcraft? Because my old massively tainted Workshop and a few other tainted Areas were disappearing at random (only Taintlevels), what is causing the tainted Stuff to disappear slowly.
It seems to me, that the Vis and Taintlevels are just resetting sometimes in the Ages/Overworld, because there was 3000 Vis at my old Workshop, were previously was 0 Vis due to me.
And don't tell me that 10000 Taint can just Disappear via flowing to other Chunks inside one hour (i wasnt often in the Overworld).
