I must be on a different version of Diablo than you. 900 resists is most definitely not low. To be honest, I don't notice much of a mitigation difference once above 850. Arcanes and desecrator will chew you up even if you have 1500 resists.
If you think the difference between 900 and 1500 is "negligible", then i feel bad for you.
And as someone pointed out, a human player can get by easily with even 600-700 resists; however as a bot you have to vastly over compensate.