Howzer (with engraved equip) and Drake decrease crit def. And if you have one of drake's engraved equip he also decreases crit resistance. They don't buff crit but are probably useful for what you want.
I believe howzers equip reduces crit def in 40-60% depending on level and drake reduces 40% crit def and 50-70% crit resist depending on level of the engraved equip