Alternatively, give Lost Island Hardmode a go. I think that would be a bit tougher than Athiss
Yeah I like the idea of Lost Island HM. Though my immediate worry with that is Sav-Rak. Staying alive for us relies on near constant DPS for heals so running around pressing buttons and being beat on instead of whacking the boss spells doom.
We can't outheal the damage for meltdown, and there are far too many stunlocks for effective healing.