The high dex checks were a bit of a compromise if I recall.
Previously you needed the "Use poison" feat. Which was exclusive to Assasins and (I think) Blackguards (unholy champions.)
The compromise was made because well... if limited to Assasins and Blackguards no one on the server would be able to use it.
I'm not sure, but is a dex check part of the way the "Use poison" feat worked? or is it auto success with the feat?
I'm thinking that non-good druids and rangers would also be fond of using poisons since they are natural, and the dex checks would be very difficult for most druids and many rangers to make. Also Clerics of Ca'duz especially, and perhaps clerics/followers of other less than LG dieties would find poisons appropriate.
Perhaps a feat that gives a +5 bonus to dexterity checks to apply poison could be created with a non-good prerequisite. I'm not sure if a +5 bonus is enough to be "feat power", it depends on what the DC's go up to, perhaps it should be +10.
Or maybe make the "Use Poison" feat available as one of the level 10+ special rogue feats.
I think followers, or at least clerics of Ca'duz should get a +5 knowledge bonus to dexterity checks to apply poison

-TV