hong said:
Just to get back to the original topic....
Mearls, you mentioned that the invulnerable pet caused you difficulties, in that anything that had a chance of hitting it would automatically hit everyone else.
I'm curious about what the dinosaur had on it that made it unhittable? Also, someone mentioned in here that the solution to an unhittable target is to switch to another tactic that doesn't involve (physical) hitting. To what extent do you consider this a valid approach in design terms? Ie, is it good/defensible design to allow someone to get a super ability if it's balanced by a weak spot/Achilles heel somewhere else? Would your answer be the same if it wasn't physical AC but magic-related, eg unbeatable SR?
I have no idea what the pet had that gave it such a crazy AC. I imagine it was simply a combination of notoriously.... interesting... mechanics, such as the druid's pet, and the druid in general, along with some stuff from Savage Species. Keep in mind that this game is pretty much an excuse for people to make ridiculous characters to pit against my equally ridiculous giants.
D&D already gives you a trade off of strengths and weaknesses on the class level. Extending it elsewhere is dicey. Races are a good example. A +4 Con isn't balanced by -4 Int and -4 Cha. Anyone who takes such a race simply avoids classes that need Int and Cha.
On a similar level, giving someone a great AC but balancing it with a bad Will save is problematic because it pushes the issue on to the DM. To challenge the character, the DM needs to throw monsters that force Will saves at him. How often is enough? Every encounter? Every other encounter?
The underlying genius of the class system is that it requires the players to work together to mask each others' weaknesses. Trade offs on that level are fine, because the adventure challenges the party as a whole. Trade offs on a PC level are more problematic, particularly when you let someone pick strength A that comes with weakness B. The smart player simply minimizes the weakness and emphasizes the strength, like with the race example I gave above.
I think balance works best when you look at equivalent options and weigh them, rather than by taking an option and putting a counter on it that rests in another area.
OTOH, you can balance by placing the cost in the correct position. A bonus to AC for a penalty to a Will save is bad, because the two aren't really equivalent. The situation that calls on AC has nothing to do with Will, and vice versa. For example, imagine a feat that gives a +1 bonus to AC, plus the option to gain +4 AC against one attack in return for taking a -4 penalty to AC until the character uses a standard action to regain his defensive focus (or whatever). In this case, the penalty ties directly to the area that the feat serves, hopefully provoking an interesting decision.
(Obviously, that's not the best feat in the world, but I hope it illustrates the idea.)