Yeah this probably needs to be in the Campfire somewhere.
Smiting is good for 2 things(imo):armor ignoring damage and undead. Vs. undead is obvious, the armor ignoring part is very nice for other classes.
The reason its very easily combined with protection and healing is for survivability, because there are 2(at least) ways to deal damage as a smiter: offensive and defensive. 55's operate off of letting the enemy hit themselves against you til they die. Due to the highly defensive nature of this build, its very popular. It also gets around the big problem with smiting: recharge times.
When you go to make your build, recharge times are the things to watch out for(besides the obvious energy usage).
But that's just my 2 cents
