Unfortunately it's not possible to skip the 2nd boss. You can clip out in various ways, but the 3rd and 4th bosses aren't spawned in yet. There is however a way to speed up the 2nd boss: By hitting the gong the 4 times it becomes active.

After the 4th time, you can jump over a large invisible wall with a triple jump + dash + backflip. I found this to be easier with the Vrykul Drinking Horn toy active, as it makes your hitbox slightly larger.

Then you can align yourself with the corner shown and clip out, and kill the 2nd boss from the outside. This is easy with DH and Evoker, but any class can do it as one of my DK friends demonstrated that he just jumped precisely and got it. Some class abilities that make it easier: Druid Travel Form Wild Charge, Hunter Disengage, Priest Levitate, Mage Slow Fall.