Well, if any change had to be done i'd say that they could... I don't know, shorten Provoke's range to match that of Shield Lob?
Either way Provoke is fine in my opinion, at least from my little experience as a tank. As a Gladiator on Cutter's Cry I was having the most awful run against the Chimera and I learned one thing, going Provoke -> Shield Lob is enough to regain tanking capacity in one GCD cycle even with the lancer going off at it like a madman. Presumably even moreso had I had Shield Oath