[PLD] Change Cover (PvE) to match Guardian (PvP)

[aodhan_ofinnegain]

I'll be honest, this change wouldn't make it anymore useful than Cover. The gauge cost is the single reason why Cover is useless, especially when compared to Intervention. Overlooking the gauge cost, Cover is significantly better than Guardian, as Cover doesn't cause you to move, while if you were to use Guardian, it would potentially screw melee positionals if you used it while holding threat, or may screw up execution of a mechanic that is position based. Only way to improve Cover, is either remove the cost, or add damage reduction to Cover, making it as equally worth using as using Intervention.

Guardian makes a lot more sense in PvP and sounds really good, but it would not be that great in PvE.