Are they aromatic blends?
A lot of aromatics will have the goop that makes them never really dry out and are almost garunteed to gurgle and leave a wet mess in the bottom of your pipe.
If drying them out and smoking slowly don't work then it's no fault of your own. Blame it on the goop.
You might want to give a higher caliber of aromatics a try? I could only reccomend Lane Limited's selection.
We do have a few aromatic specialists here who should be glad to steer you in a good direction.
If it's an english blend... then dry it out more and smoke slowly.
And your first assumption of darker tobaccos being bitey and more wet is wrong if it's an english blend. There are plenty of all natural tobaccos that are black as night, but just have been processed in a way that darkens them to bring out a different array of flavors.
As for the blends that bite. I haven't come across a remedy yet that will fix a blend that bites.
To be clear when we pipers talk about a tobacco "biting" it's not the heat or steam that we are refferring to. It's just a chemical reaction (or PH levels) between the smoke and your mouth. Some blends will just bite you and you can't smoke them because it literally hurts too much to keep smoking the blend.
Keep pressing on and trying every style you can get your hands on. Won't be hard to find some great smokes.
Welcome to the forums and good luck on your journey. :
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Edit: Lawrence is correct that a mouthful of steam won't feel very nice on the tongue/mouth, but steam and a tobacco that bites are two separate feelings. Neither are enjoyable.