Jack99
Adventurer
This is how it has been for 4½ edition (or however long you have needed to use fire against trolls. It has never been an issue in my campaigns.
The first couple of times the players meet trolls, they do not know (unless they pass the appropriate checks) what a troll is capable of. As they become higher level and more experienced, they have easier access to the knowledge and can act upon it, and thus the troll regen becomes a non-issue.
In short, if one of my players ever tried to use an at-will fire to cancel out regen without getting word from me that it was okay for his character to do so, it would be stopped immediately.
Cheers
The first couple of times the players meet trolls, they do not know (unless they pass the appropriate checks) what a troll is capable of. As they become higher level and more experienced, they have easier access to the knowledge and can act upon it, and thus the troll regen becomes a non-issue.
In short, if one of my players ever tried to use an at-will fire to cancel out regen without getting word from me that it was okay for his character to do so, it would be stopped immediately.
Cheers