I completely disagree.
Obviously the growls work great on Heir Apparent, since it's more of a Heavy Metal song. However, I think they also work great on TLE and HP. TLE is a very bizarre song, so it's not surprising that things seem out of place at first. However, the more you listen to it the more you start to appreciate it.
I think most people here would agree that Porcelain Heart is the most "Blah" song on the album. Now, obviously part of the reason is it's slightly more commercial and less proggy than typical Opeth (see: The Grand Conjuration), but I think the lack of growls also make it a little more dull as well..
Don't get me wrong, I still think PH is a fantastic song, and probably a smart move by the band (Good song to get people interested in the band). I always listen to the song when I'm listening straight through, but I never really find myself going straight to it as I do with HA, TLE, Burden, and HP