Lets take your logic and apply it to something else:
Doing 500 fates takes more skill and is more difficult than doing 1 fate.
Doing a 6 hour dungeon takes more skill than a 15 minute dungeon.
Doing Eureka for 500 hours takes more skill than 1 hour.

None of these are true. The skill is in learning the mechanics and practicing so you have the muscle memory to do the mechanics while you DPS to beat the enrage but once you have that the only thing making it take longer does is turn it into a dull grind. You're stripping the fun out of it, not making it more skillful.

Part of good encounter design is setting a good time limit for it. 30m is far too long for that type of content.