Currently this game has a tickrate of 0.6 and much of the game code is tied to this rate so changing the tickrate for the entire world is a lot of work and would increase server costs. For comparison a game like League of Legends has a tick rate of 30 ticks per second.
As to not overhaul the entire game one solution could be to host boss instances at a higher tick rate. It doesn't have to be ridiculously high, just something to make movement more smooth and actions more responsive.
Thanks for your response Tenebri, I would really like to see that implemented for the longevity of this game. If its too hard to do for the entire world I guess a limited implementation for instanced areas could be something to consider.