Enchantments proc from heavy/light attacks, and all abilities in the relevant weapons skill line.
AOE DOTs however (Blade cloak for DW, Endless Hail for Bow, Elemental Blockade for Destro Staff - and the other morphs) are able to proc an enchantment from offbar. That is, you have a staff with a zerk enchant on your backbar. You swap to backbar, you cast elemental blockade, zerk is triggered for 5 seconds, swap, wait for zerk to end, it gets immediately re-procced by the elemental blockade, even though you dont have that enchantment on your frontbar weapon.
It's a key mechanic for PVE and one of the reasons why stamina players are pretty much completely stuck with bow offbar.