I would imagine smoking dottle would be similar to smoking a cigar that was put out and relit. To me it has a stale, old smoke flavor that completely takes away from what the tobacco is supposed to taste like.
I will admit it does have a certain resin-y and heavy quality to it kind of like cigar leaf all the way through. But its not too bad. Its very similar to relighting a bowl you smoked half of and let sit for a few hours. The flavors meld and kind of evolve because you essentially lightly stoved the tobacco. Toppings do drastically diminish but I don't do too much with aros.
I have found that quite a few blends get better in the last half of the bowl, most make a lateral change, admittedly some get worse and very few don't change at all. If it's a blend that gets drastically worse in the last half of the bowl I won't add any of it to the mystery jar or smoke more than a tin of it. Roughly only 1 in 12 fresh bowls aren't smoked in their entirety, so I don't always add to it.
Also worth noting that I smoke what I am assuming is wetter tobacco than most. The only things I will regularly even think about drying before packing are gawith blends and even then, no more than 10-15 min at most. If its wet I just take my time getting a good light and take it slow throughout. I would also assume that the moisture content of the smoke sort of "cases" the tobacco at the bottom of the bowl which somewhat prevents it from being stale like a relit cigar.
I enjoy a variety of blends and hardly ever repeat the same blend twice in a row. I keep about a half dozen tins in a rotation, all different, and smoke 2 to 5 of them per day. The contents of the jar are always changing.
The main draw of the dottle mixture isn't that it is dottle, it's the mixture of it. I enjoy being able to light and ponder a bowl that starts off as a stout VaPer, then hits a patch of cavendish before rapidly transitioning to the dark fired of black twist for a while then comes what seems to be a mixture of tonquin topped burley and latakia then back to DF but different now, sweeter and richer more like dark plug, then out pops grosemoor and finally finishing off as a mutt of haunted bookshop with the light ghost of all that came before. It's a wild ride and always unique. Definitely not for everyone though.