I'm going on recollection now, ( away from my notes), but as I recall if you get too hot you risk "smoking" the tobacco, meaning it will be combusted in your oven....
Perhaps if you have a food dehydrator you could toss it in there and see if it will dry out.
I talked with a couple of tobacco sages yesterday and I was informed that it is not uncommon to find an antidessicant additive in even untopped "English" blends. This is to keep the product at a stable consistency of moisture content. (I think it may have something to do with the fact that water is cheaper than tobacco, call me paranoid)..
Propylene glycol is the most common additive, and it has been in use for some time now.
http://www.tobaccoproducts.org/index.php/Propylene_glycol
http://www.puff.com/forums/vb/general-pipe-forum/135584-propylene-glycol-pg-pipe-tobacco-pro-con.html
The second link hit's your nail on the head I think...
"Propylene glycol and other humectants are heavily used in drugstore tobaccos and jar blends to keep them from drying out. Some of these tobaccos will not dry out if left loose on a newspaper for a week. Premium blends, however, usually do not have as much PG as drugstore blends, but it's hard to find one that has [absolutely] none. [...] Proplylene glycol can prevent tobacco from drying out and helps retard mold growth. It is, however, a chemical that many of us would rather not have in their tobacco. Discovering that a favorite blend has a small amount of PG in it is not going to keep me from buying it. But knowing that a blend is treated with PG and other chemicals might very well keep me from even trying it."
"Propyline glycol is not the evil chemical that some believe it to be, but, like anything else, it can be abused, and often is in "cheap" tobaccos. Glycerin, glycerol and alcohol were widely used in the past in flavoring tobaccos. Why so much of the industry switched to PG is a question that can PROBABLY be answered by economics.
In a relatively pure state, PG is viscous, and somewhat slimy to the touch. It binds readily with water, and is often used in humidifying units in cigar humidors to maintain a fairly constant relative humidity of about 70%, considered ideal by many. It has a distinctive sweet taste and substatially lower toxicity than ethylene- and diethylene glycols, but high ingested doses have correlated with hepatic and renal diseases. Don't drink it. If your tobacco is sticky, and it won't dry out, you've probably got a good dose of PG present. It's also found in oil-free salad dressings, and a lot of cosmetics.
And, no, I don't use it, though tested samples of some ingredient leaf have shown small amounts present."
GL Pease, 2001-12-14
Hope this sheds some light on what you have going on...