Bump
Q 224 What's the average AC (standard, flat-footed, and touch) the average 20th level character should be able to hit? What should be the highest? What should a gish character be able to hit?
Thats pretty vague... Id assume a well built Gish will have a BaB of 16. So then depending on what kind of character they are you can stack on buffs/items as needed.
If your making a npc for your players to fight then Id make it somewhere like high 30's. My players recently faught a ur-priest gish at 12th level who had ac 31 and they still managed to take him down.
Vague is what I was going. I know the players will be wanting to gish themselves out, and I want to be fair for AC. I don't want it so high they can't possibly hit, but I don't want it so low that they'd need to roll a 1 to miss. Right now I've got an "end boss" character that'll have 57 AC without really trying, but if it's too high I'll look to cut it down to something more reasonable. Touch and Flat-Footed are around 40-42.
Have a couple of options for AC only buffs that you can choose whether or not to give him after you get an idea of their to-hits from other encounters.
You can do it sneaky as The_Mad_Linguist suggests or just straight up ask them what their accuracies are. If your group must believe they aren't on a strict no progress level treadmill as far as party BAB and enemy AC goes, do it sneaky. If your players have been DM's before or just know what's up because they aren't stupid, ask them straight up what their accuracies are so you can easily make AC values for monsters. If they're newbies, do it sneaky so they feel powerful and whatnot.
I keep their accuracy percentage at about 7/10 to 8/10. That way the heroes feel heroic and don't miss all the time.
If the difference in combat characters' accuracies is more than 10, you literally need to fix something. Other wise combat ability is simply much too different when using a d20. Same for Armor Classes. I would say a difference of 5 for accuracy and AC is the biggest you should allow.
If there is huge difference of more than 5, you need to talk to your players about in-party balance. One combat character can't be sporting +10 more accuracy or AC than their friend. Players with lesser characters will rapidly and permanently feel less powerful and thus have less fun. Having less fun is bad since DnD is a game, so be upfront and talk openly about this issue. Preferrably before character creation or the campaign starts. If your players aren't sociopathic ass holes, they'll forgo ungodly AC or ungodly accuracy so everyone can have fun instead of one or two stealing the spotlight every session. If you players are sociopathic assholes that willingly stomp on other players so they can feel more powerful, be a sneaky bastard DM to make things even. They'll enjoy the challenge.