Save or Dies and Hit Point Thresholds

The Spells document in the March 2013 document has a few save-or-die, save-or-suck spells. A few of them seem a little unbalanced considering the level, hit-point threshold, and effects. Polymorph in particular caught my eye as a pretty low-level save-or-die. The design principle seems inconsistent on whether the HP thresholds should be for current or maximum hit points, and whether that threshold disallows a save. I'm including a very rough table of the general effect of each spell, for comparison's sake. The effect listed is just for a creature that is beneath the listed threshold and fails the save, if there is one.

LevelSpellHP ThresholdSaveEffect
Wizard 1Sleep5d8none1 minute sleep, multiple targets
Cleric, Paladin 1Command30noneCommanded for 1 round
Druid, Wizard 4Polymorph150 maxWisdom fullSheeped for 1 minute
Druid, Wizard 5Feeblemind150 maxWisdom fullFeebleminded until heal
Wizard 6Disintegrate60DexterityDeath
Cleric 6Harm14d6none1 HP for 1 hour
Cleric 7Holy Word30Charisma full1 hour stun, multiple targets
Wizard 7Finger of Death40noneDeath
Wizard 9Power Word Kill50noneDeath