If it's a lone WAR and they Holmgang me, I pop Equa and chain Bene II through the Fell Cleave spam, or just spam my instant shields on AST and wait it out. You can still cast stuff on yourself while you're 'ganged, you just can't cast on the WAR if he grabs you from behind.

If a WAR snags me with a pile of buddies right behind him, I Purify, Sprint, and GTFO. Works pretty much every time. Always makes me chuckle seeing them standing there impotently while I leave them in the dust...I imagine them shaking a fist at me like a cheesy cartoon villain as I roll out.