You can also get the boss out of position or get people cleaved faster than any other tank.
He's also coughing up both of the amazingly useful PvE Guardian set bonuses (better CDs and 20% better Blade Barrier) for a 10% increase to damage 20% of the time (assuming he only Leaps in after Leaping out) and that 8% heal every 20 seconds.
But, yeah, I have to wonder what content the OP has actually done as a tank: if he's *that* devoted to constant leaping, he's going to have a lot of cleaving going on though I'll admit he might have an easier time of threat than most Guardian tanks thanks to the increased damage and near constant threat drops. Even so, my gut says it would be a net loss in survivability and early fight threat (re: the only kind that matters) thanks to the lost GCDs (Leap out for no damage and Leap in for marginal damage). I can't imagine clearing any progression content with all of that leaping about.