I'm fine with higher-level characters being immune - or virtually immune - to non-exceptional poisons and diseases.
I had a 14th level dwarf character once with a Fort save of +20 or so and the feat that stopped natural 1s from being an automatic failure on Fort saves, and - aside from kicking ass in a fight - he was a lot of fun to RP...
He'd do stuff like get shot by a poisoned projectile, pluck it out, lick it, roll the poison around in his mouth with the expression of a wine connoisseur, then go "Oh, come on, really... wyvern poison?" and proceed to hurt the attacker while shaking his head in mock disappointment.
I had a 14th level dwarf character once with a Fort save of +20 or so and the feat that stopped natural 1s from being an automatic failure on Fort saves, and - aside from kicking ass in a fight - he was a lot of fun to RP...
He'd do stuff like get shot by a poisoned projectile, pluck it out, lick it, roll the poison around in his mouth with the expression of a wine connoisseur, then go "Oh, come on, really... wyvern poison?" and proceed to hurt the attacker while shaking his head in mock disappointment.