Early in Rise of Shadows, it turned out that Paladin isn’t in a great spot. A full Secret deck failed, because despite a powerful early game, it fell off heavily in the mid and late. Dragon Paladin, on the other hand, just doesn’t have enough synergies to work. But the class was saved by the Boomsday Project, when Mech Paladin turned out to be working.
Mech Paladin, also called Secret Mech Paladin, because of the early game Secret package it runs, combines the strengths of those two builds. Early game Secrets provide a way to survive until the mid game, when Mech synergies take over. Since you don’t run any small Mechs, it also makes Kangor's Endless Army extremely potent, since you always revive a solid board.