Physical attacks hit Health directly, except what is blocked by Armor. Physical Attacks will ignore Focus, so they will not break a channel… unless you kill ‘em first.
The only type of damage that can break Focus while a target is channeling. Any damage that remains after the Focus is broken, is counted against Health. If a Mental Damage attack is used against a nonchanneling target, the damage hits Health. Mental Damage ignores Armor.
Usually encountered though status effects such as Bleed and Poison, True Damage ignores Armor and cannot be negated in any way.