PALADIN Cover ability (taking damage of party memeber) question

[Absurdity]

Does it take damage before or after mitigations of party memeber applies (like another party Rampart or something)? Or do I take clean damage intended for party member before any manipulations? Later, isn't it?

It entirely ignores the covered target (unless the mechanic is scripted to ignore cover instead), that means only your own buffs and debuffs factor into damage calculations.