I find that giving a 1 point level based bonus to AC at every even level and +1 to all saves at 4,8,12,16, and 20 to be roughly balanced with the effects of magic items.
I broke down a couple of suggested levels and it came out slightly in favor of defense which was fine with me.
You can even do away with the save bonus if you use action points.
Do this and if you assume any magic items are a power up rather than a necessity and it should work well enough.
The easiest way to deal with casters is to allow a maximum of 1 caster, full or 3/4 and 1 (or 2 if there are no full or 3/4 casters) 4 level caster per party of 5.
