If you read enough complaints about EX, it becomes very clear they consistently resist taking action on disputes, no matter what the circumstances. They are well aware that only a tiny number of consumers will ever bother to file a lawsuit regarding a legitimate dispute. So 99% of the time, consumers get the "previously verified" letters and other brick walls thrown up in reaction to their disputes. It is a very efficient method for EX to allocate their resources, and their policies are beneficial to creditors and collection agencies because the OCs and CAs are able to maintain pressure on consumers by affecting their credit reports. Remember, OCs and CAs are Experian's customers, and EX creates and sells a long list of products to assist collections.
IMHO, the least aggravating way to deal with an EX problem is to (1) dispute it the usual way, understanding that you only have a 1% chance of success, (2a) if the dispute is substantial and worth a lawsuit, retain a lawyer, send EX an Intent to Sue letter, and file suit if you don't get a response (in many cases, EX actually do respond once they believe you might file suit), or (2b) give up until the item falls off your CR, and accept that your EX score will be depressed until that happens (if the OC or CA don't change their reporting, you are banging your head against a wall if you continue to try to dispute with EX).
My DW has a bogus collection on her EX report. We successfully had two instances of the same bogus collection removed from EQ, but hit the usual dead-end with EX. Her FICOs are 771, 761, and 690. Guess which is EX. The collection is only for $44, and mortgage lenders and auto lenders disregard it, so we will just ignore it for another year or so, even though it's annoying to see it on the CR.
By the way, the staff at EX aren't idiots, they're Vogons ...