Well, I still stand by the Treasure Room being the most pointless, but the only reason I think it's more pointless than the Heart Room is because the Heart Room was already there for most of the season— why have an equally simple room next to it? The Season 1 Observatories and Throne Room were just as bad, though, by virtue of the fact that their "objectives" required no skill, no chance and no time consumption.
On the other hand, I'd say rooms like the Room of Golden Idols, the Treasury of Golden Orbs and just about every room below them fall under "wasted potential." They weren't inherently bad concepts (except for the Spider's Lair, of course), but because of the paths that were designed, the actual objective was barely ever used for the Room of Golden Idols, and we barely got to see how hard it could be to navigate up through the Swamp or whatever. Rooms like the Treasury and the Bamboo Forest were better concepts for offering more of a challenge, in my opinion, but apparently they were too good to last, meaning the Holes of Python was probably the only well-designed, well-thought-out and (close-to-)well-used room in that entire pillar in Season 1.

I usually discount the pit rooms because they tend to involve either a critical choice of paths, some form of navigation (at least the wall climbing required a bit of skill) or an actual objective, but it's a shame the Troubled Bridge didn't have some sort of hindrance like the bottom half of the room. It's not enough to make me really write off the divided pits as bad rooms, per se, but it does bug me a little in hindsight...