[Rhino]? Iron Skin? What's that, I've got [Revenant].....
This build let's you get over 25+ Mesmer Skin stacks, which is more than enough for any type of content (especially Index and bosses).

-Focus: Zenurik (Inner Might+Hardened Wellspring) Provides and extra stack of Mesmer Skin and free ability cast every minute

-Helminth:
1st choice: Empower - of course gives an extra stack of Mesmer Skin, cuz why not?
2nd choice: Xata's Whisper - broken damage that makes any weapon one shot everything

Use Corinth, Felarx or/and [Laetum] for Index to obliterate anything in your path