Anyone that is already using Glider already has the ability to see any of the encounters in the game. While the purpose of other copyright-circumventing devices is to display content the user hasn't economically paid for, with Glider the user has already paid for seeing all of the content.
The intended purpose of the law was to protect revenue streams of companies by ensuring that users pay for access to copyrightable works. Blizzard is using the law in this instance to protect their revenue stream by preventing other players from quitting the game, not using it to ensure that unauthorized users don't have access.
The real problem is that Blizzard is saying 'This using broke the cheating rule, therefore they were in violation of the EULA, therefore they weren't an authorized user, therefore any attempt to go around that protection is against the law', but glider's primary purpose is to allow cheating.
(A) is primarily designed or produced for the purpose of circumventing a technological measure that effectively controls access to a work protected under this title;
Circumventing Warden is not the primary purpose of Glider, but rather is a secondary function in order to allow the primary purpose.
"Spock, did you see the looks on their faces?" "Yes, Captain, a sort of vacant contentment."