I don't like the idea of simply making Shield Swipe instant because it would dramatically favor Block Rate shields. DRAMATICALLY.
Plus, we already have a stun with no cooldown AND a silence.
The pacification effect would simply be FAR too powerful if it were off the global.
Paladin is really hurting for an off-tanking combo.
As is now, the RoH combo actually does more damage than the Riot Blade combo AND using the Riot Blade combo runs you out of TP quickly.
I say just make Shield Swipe the third skill in the Riot Blade combo, up the potency to ~250 when combo'd so that the Riot Blade combo does more total potency and costs less TP per global than the RoH combo, and call it a day.