Well, on another thread I established myself as an advocate of save-or-die. I have a problem with Harm: it's no-save-and-die.
Let's be fair. A simple Harm, with a simple touch attack, followed by a Quickened Inflict Wounds, can take down any living creature, great or small, with no benefit of a save.
In this, it is unmatched by any other spell in the game. All of the other instakill effects allow a save, with the exception of Power Word: Kill, which has a hp cap. No other spell in the game, and no other effect in the game (except Vorpal, but that's a different thread altogether) has the same sort of damaging power that Harm can dish out.
As for the Harm/Heal dichotomy, this is a nonsense. There is no 'parallel' dimension in DnD. Is there a 9th level wiz/sor spell that raises people in a 30' radius spread to mirror Wail of the Banshee? No. Is there 'Healing Barrier', which heals 1d6/level in an area for 1 round/level? Of course not. Spell symmetry, clearly, is a nonsense.
The counter-arguments have, for the most part, relied on pure assertion. There has been the necessity for a touch attack (easy at high levels, and if this fails, just go again!). There has been that Harm doesn't kill you (+ Quickened Inflict Wounds: you're dead.) There has been the escape-clause of flying (circumvented with wizardly aid, potions, Greater Aspect of the Deity, Wings of Flying, etc.). There has been 'getting up to the big dragon' (no big deal: you take one hit, then make an easy Conc check to cast defensively).
Essentially, Harm is broken as written. I allowed a *Will* save (in line with Inflict Wounds) for 6d8+level: more damage than Slay Living, comparable damage to Destruction. I think my correction is fair.