Tinkers knowing where subdungeons are makes it a lot easier to scum for treasure subdungeons. I'm not sure if that's a good thing - getting the armory at level 1 is a huge boost, especially on a purist run, while the gold vault is nearly always a big boost, so it's sub-optimal for a Tinker not to scum for them. (Perfectly optimal play would of course require all classes to scum for them, but considering all of the other things you'd be scumming for as well, perfectly optimal play involves tedium bordering on madness.) The monster room, on the other hand, is nearly useless unless you have lifesteal, a Blue Bead, or are worshiping Tikki Tooki. (Taurog, too, I suppose, but Tinkers hate Taurog almost as much as Vampires hate Glowing Guardian.)
On a related note, I think it would be nice to have different kinds of entrances for the treasure subdungeons - ones that don't require wall-destroying powers, which not all classes have access to all of the time. Maybe the gold vault is guarded by a special monster (maybe a Leprechaun)? Maybe one requires you to pay (via a specialty shop) to enter? Maybe one of the walls surrounding the stairs is revealed to be a secret passage if it's hit by LEMMISI?