Perception is everything. To my ears, Hampson sounds as though he's trying to compensate for a small amount of vocal degradation by over-interpreting everything; often times conjuring up phrasing and diction that sounds over-done, mannered, and too fussy. If anything, it sounds to me as though he's compensating by trying to put too much heart into everything.
By the way, one of my very best Mahler 3rds is a "pirate" of a live performance with Welser-Most/Cleveland. The mezzo wasn't great, but everything else was fabulous.