To all the Tanks 'fishing' for CT instances...

[Nalou]

Don't use Duty Finder for Crystal Tower.
Build a 8 man party with Party Finder, and then use Duty Finder to find 2 more teams.
Problem solved.

[Phreak]

Don't use Duty Finder for Crystal Tower.
Build a 8 man party with Party Finder, and then use Duty Finder to find 2 more teams.
Problem solved.

This doesn't solve anything considering any one of the other two teams could include a Tank or even a Healer that is 'fishing'.

What they need to do is what World of Warcraft eventually ended up doing and hiding the progress of the run, make 'join in progress' the norm and not just an option, add in a system that tries to push you into a fresh instance if the one before wasn't.

A few other ideas I can think of would be that if you personally withdraw from a que you must wait 2-5 minutes before being allowed to que again or add some sort of penalty for multiple withdrawls.