Same experience as the OP. Brewed a tripel with SG 1.083. It finished at a perfect 1.010. The beer still came out sweet tasting even using just 0.5lbs of crystal 10L. I can definitely taste a bit of alcohol hotness in my beer even though I fermented at 60F the entire time. Unlike some well made examples of the style that hide their alcohol a bit, mine is pretty obvious.
So if I recap this thread, people seem to think the perceived sweetness could come from three possible sources: use of crystal malts, high alcohol content and the yeast strand (westmalle) phenolic profile.
Here's the grain bill I used.
11.00 lbs Belgian Pilsner Malt
1.00 lbs Malted Wheat
0.60 lbs Brown Malt (wanted to use 30L amber malt but got duped in buying this instead)
0.50 lbs Crystal 10L
2.00 lbs Turbinado sugar
So the question is, if I want to reduce the sweetness of my next attempt at this beer, what should I try first? Switch yeast strand? Nix crystal and mash a degree or two higher to compensate attenuation?