Of the ones I've actually killed, Maloriak is my favorite...good teamwork fight, face paced, and there really isn't much of any significant RNG that you can't be prepared for and deal with accordingly.
I won't say hate, but I'm not a big fan of Omnitron..as a hunter that can't interupt or anything, there really isn't anything special we have to do other than slow adds when they come up and avoid the mechanics everyone else has to avoid when they come up, and I very much enjoy having to carry my own weight and there is not much I can do other that avoid taking damage and pewpew lots....and its a very long fight. So far, the rest I really rather enjoy.