the asus dc2 290 is likely using the digi+ asp1212 voltage locked controller. i dont feel putting a water block on a card with a locked controller is worth it at all. find a card with a beefed up unlocked controller, upgraded mosfets and vrms, and a binned chip... and would be nice if said company's card can be bios flashed without voiding the warranty, along with the water block also not voiding warranty.
there is nothing wrong with your controller, except under water with any decent pump and rad, your going to hit a voltage bottleneck long before you hit a thermal bottleneck which is not what you would want.