For the reasons you give its nearly useless for PC clerics, but it is ideal for evil NPC clerics. I mean, if Fus-Ro-Dah is the verbal component/evil mantra of an evil priest, each use results in a progressively scarier effect. A door slams shur, a peal of thunder, candles change color, the priest's voice becomes impossibly loud, the ground begins to shake, the colors go back to normal but the priest's eyes glow the color the candles were.
In a low-magic setting, this is like distilled cult-leader.
However in settings where magic is more common thaumaturgy is better for bards than priests.