Imaro, that's just silly. If an ability works most of the time, the player most certainly can observe, that, most of the time it works. Can they absolutely predict if something will work? No. But note players are in the same situation when rolling to hit in combat. They can't predict what will come up on the die (and if they can, why are playing D&D with them instead of being in Las Vegas??!)
No it's really not, but perhaps I didn't explain it as well as I thought I did. See your presented argument is false...the reason their ability doesn't work in the example is because the DM doesn't want his plot, adventure, etc. ruined... this is a totally arbitrary reason and, since the DM lies to the PC's about why the ritual fails... how do they know when they're ability infringes on the DM's plot and when it doesn't... thus at random times, the abiltity thay have won' work.
When rolling to hit in combat, I know that if I roll over a certain number, I will hit the monster...In the ritual example, nothing I did was going to change the outcome of that ability, there was no chance for success at all. Do you not see he difference in these situations?
The existence of exceptions/extenuating circumstances are not enough to transform a PC ability into a plot device. Note that being immobilized does not make a PC's speed into a plot device.
No but once the DM has decided for plot purposes that an ability works or doesn't work, it has in fact become...a plot device and no longer a character's ability.
I allow PC's to do things outside the scope of the rules all the time, so that they can better play the characters they envision, but as for your specific example, I haven't done that.
You're switching up what I asked...I didn't ask you if you allow PC's to do things outside the rules, I would assume most if not all of us do. I asked you if in the middle of a fight, let's say with a black dragon a PC turned to you and said, "My character's fight with the dragon isn't unfolding like I want it to, and I ran into this fight ill-prepared... I don't want the dragon's breath to recharge for the rest of the fight.", would you allow this...without any input or even letting the other PC's in the group know.
OK. Limiting/nerf scry doesn't have to be about preserving the DM's plot/story. It can also be seen as a way of excluding certain solution sets in order to direct players into other solution sets. The best example of this are certain dungeon rooms in classic 1e tournament modules. Certain spells don't work in these rooms. This isn't to preserve any kind of plot --because there is none. It's done to force the players to solve the chess-piece puzzle that makes up the room's floor.
This smacks of "DM knows best what fun is" type arrogance. My opinion is that this is usually fun for the DM... and not so much for the player who had an ability he chose and wanted to use shut down. I don't think PC's tend to take abilities so they can... not use them. Of course I could be wrong and that could be exactly why they do it...I guess.
And for the record: I have no story to tell as a DM.
Well then why would you shut down a possibility, instead of seeing where it can take you and your players?