Perish Song, it's completely uncounterable. Just grab a Murkrow or Lapras. Switches out? No prob, loses Sub and eats entry damage if applicable. Last mon, can't be Roar'd? No prob, it has 3 turns to live, you win. Murkrow has Prankster for Perish Song / Roost, and Lapras is absurdly bulky and doesn't care. Dewgong is the same as Lapras, but comes with Encore, Disable, and Thick Fat at the cost of being statistically inferior in every way.
Heatran's gone, which means it fears almost nothing.
Or get something with Trick + Specs, like Espeon. It has to switch moves every turn to succeed, and Specs denies that at no detriment to you. Pressure invalidates Encore so try to avoid that.
edit: Rest would keep Burns / Toxic off your balls.