Trainz said:
You know what, I wouldn't mind that much leaving Blasphemy as it is. It is weaker than holy-word, but still. What would need to be done, is to not allow circumstances where it can be cast once per round ad infinitum. That creates an unmanageable situation.
Well, that comes to the unique nature of the spell. For most creatures, having a spell 3x day is the same as having it at-will, because for encounter purposes, he probably will either cast it as much as he possibly can and then die. A beholder will use it's eye-beams as much as it can, but if you limited it to each beam at 3x day, I'm not sure that the players would necessarily notice the difference unless it was sniping them from an unreachable location.
But Blasphemy is a spell that, for level equivalents, merely delays the battle. As such, it becomes a different situation when cast at-will then a meteor swarm, for example. Especially since there are more ways to counter the latter. But I suspect that some simple parameter change would make it more palatable...perhaps to reduce the burst radius or give a save. An evil cleric with the ability to scribe scrolls could replicate this behavior, so even without it being at-will, it could still become an issue if you find it problematic in repeated castings.
I agree that the Balor makes it problematic under certain situations...but so would a kobold who's manipulating a sphere of annihilation, if the DM ambushes the party with that. All of which is getting away from the original intent of the thread, I think.
From a game standpoint, there are several classes of spells that can make verisimilitude difficult. 3.5 has gone a long way to addressing the problem with scrying, one of the most egregious problems (while simultaneously making wise rulers more attractive and increasing the market value of lead

). The ready availability of the many healing spells, crafting spells and transportation spells are all spells that can be problematic if spellcasters are largely available and easily accessable. I would highly recommend Magic Medeival Society: Western Europe for a look at how a standard D&D setting can be made to make sense within a Medieval context, largely using social context to make to regulate much of the activities of a game.