Doesn't look hard until you attempt it.

Basically there are two challenges : meet the 3 minute berserk timer, and pass P1.
15k boss DPS is enough to beat the first challenge, luck is needed for the second.

In P1, Elisande stacks Ablation on you. This DoT deals gigantic amounts of damage, and since adds reduce and increase the duration with their spells, and Elisande seems to sometimes forget to refresh it, it's down to pure luck.
Use everything in P1, because P2 and P3 are comparatively very easy.

Kill as much adds as possible without losing too much boss DPS, use purple bubbles to their full extent.

Music :

Position Music - Quantum (Joseph Trapanese)
Ivan Torrent - Neon Paradise
John Murphy - Sunshine (Adagio In D Minor)

Enjoy :)