If you play melee, no matter what your dmg type is, still need high OA enough to hit enemies.
If you want to play with elementals dmg and don't have high OA, just go with throwing weapon + shield/bow or dualwield throwing weapon.
Thunder Strike works best with Dualwield Throwing Weapon.
Just Physical dmg( and may be Piercing dmg too) from melee hit can crit.