That would catch up the lowest NAD, but jet the highest one ahead by 4 points. If you get rid of the improved defenses feats (all of them, from both PH and PH2), I guess it wouldn't necessarily be too dire.
What level is your fighter? Does he have great fortitude or an item that improves Fortitude? Is he human?
Cause +4 would turn that 50% into 70% which is really about the upper bounds of where your missed chance should be... and an item and great fortitude would net you another +4 which would bring that to 90% missed. Human 95%. Etc.
True, but as in your last post house rules may need to be balanced with other houserules. If you allow for a net bonus to NADs, it may be prudent to remove NAD boosting feats.
Yeah, that's pretty much just my point. That it feels like the up to +6 to NADs you can get via feat, plus the up to +3 from items, are mostly shoddy bandaids, so as long as you take them out, you're probably fine.
Just don't give out +7 over 30 levels _and_ +6 via feats _and_ potentially +3 from items/masterwork... cause that'll just go over the top.
My house rule is as follows:
+1 to F/R/W defenses at levels 5, 15, 25
+1 to one defense for which you have a class bonus at levels 11 and 21
No Paragon or Robust Defenses feats, no Epic Fort/Ref/Will feats
Great Fortitude, Iron Will, Lightning Reflexes, and the epic feats with special kickers are still available.
I'm not convinced this is a problem. It makes someone almost HAD immune. But there is still AC, and this guy really paid a lot for it.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.