I agree with Rentahamster. The classes that can equip a shield should just automatically learn shield skills at specified levels and they should scrap Sentinel as its own class identity. Maybe this is something they'll be announcing in their class changes letter.

They should go further with this for Gladiator/Marauder/Pugilist (and their upcoming Jobs if applicable) for their abilities that activate upon a block/parry/dodge and have them light up when you have the TP AND perform the associated defensive action. That way it's easier to visually tell when you can use Phalanx/Fracture/Haymaker.