I play this game on torment
and now I have seven gazer. gazer is so powerful not only it's normal damge(with correct equipment its one single shot can reach 200-300 damage same with the darkon)but also it's status effect (stun terrified null field dominated related to three kinds of res).it can easily frozen your enemy no matter what it is. so we don't need tank any more.
it also has decent AoE skill which will not cause friendly fire(like Drakon).
so for the best top tier creature I think
gazer>drakon>rotghroths