zeal has the same mechanics as fury. It wont be very good against bosses with dodge/parry/block etc.

A smiter would procc it more consistent and faster if you ask me. Its almost like the poison smiter we once had with plaguebringer as weapon.
But with a smiter you would loose every targeted benefit, such as making holy fire viable and you would have way less life and surviveability.

the only thing to get more firedamage out of the proccs is to skill with 20 armageddon (=+40% firedamage) and the rest of the points into fissure (every point makes 2 more seconds of armageddon).