I definitely have reservations about letting fighters chop through adamantine walls in one blow.
I have experience with this. ToB does not allow you to hack through an adamantine wall with one blow. Even if you ignore hardness, your half damage vs objects will slow you down greatly. A warblade can not regain his maneuvers fast enough outside of combat to make rapid progress.
My swordsage was able to get through an adamantine floor in a few minutes using a strike (IIRC emerald razor? I dont recall its name) every other round, using a full round action between to recover. This was vital because the party was caught in a flooding chamber death trap. Only one of us could breath underwater, so we were looking at a near TPK.