I long ago made it a house rule that anybody who beats the DC can find a trap, regardless of weither the DC is 20+
Then I changed the Trapsense ability. Now Trapsense grants the rogue the ability to make an automatic search check (secret, rolled by DM) anytime he comes within 5' of a trap (sort of like elves and secret doors). So the rogue is still the best trap-finder but now is not totally essential. As a bonus this encourages the party to not take 20 on searching every damn 5' square unless they have a reason to expect a trap.
Hope that helps.