Threads are already starting to complain about SEs design choice. Despite the fact that this is gonna be a 2.1 issue and will be changed in future patches, so you can queue as 24man. Here is what my FC thought off to maximize the chance of queuing up as 3 groups but getting inside CT together.

Step 1: Form 3 groups of equal setups(2 Tanks, 2 Healers, 4 DDs)
Step 2: Everybody changes their "DF language" to something specific, like French, or German(depending on what server you play on)
Step 3: All 3 groups queue up at the same time.

Step 4: Server process. DF always looks for members on your server first and based on the language picked. If they can't find anything suitable on your server, they start to look for groups from other servers based on your language picked. Then he looks for groups of any language on any server.

Since all 3 groups picked a specific language and are on the same server, queuing up at the same time, there should be a high chance of getting your 3 desired groups into Crystal Tower together.

Problem solved.