This is what the guide in question says:
'My gosh! Someone has done it. They've created the most interesting and potent spell ever. Never since D&D was a twinkle on the eyelid of Gygax himself has there been a better idea for a spell. Ten whole words. Ten. This is SO overpowered that WOTC...
The thief's ability looks a lot more powerful to me (a full turn vs one action, every combat vs 1/short rest), but even if I concede your point, I'm still not quite persuaded. The issue isn't really about whether the mystic is balanced with the cleric (which, obviously, you can only determine by...
Yeah, I can't quite understand why no-one else seems bothered by this. Perhaps I'm just missing something, but it looks wildly, conspicuously overpowered to me, especially when you compare it to the poor Knowledge cleric's *seventeenth level* domain ability