I don't have much of a problem with the Priest, but I really would like to make a suggestion about its starting aptitudes. Chiefly, I must wonder why the Priest doesn't have the Knowledge aptitude. It starts with a number of Lore skills and its recommended advances also include more Lore skills (well, training in the ones it has anyway). The Priest, also, is probably one of the few characters you can count on in the squad to actually know how to read, and more than that it seems like he would need to be receptive to certain types of knowledge in order to carry out his mission. Though the 41st Millennium extols ignorance, the priest is the one person who should know about what's out there, such that he would know how to protect his flock's minds.
I would suggest simply adding it on, but the Priest already has 7 aptitudes, which is one higher than the baseline. In such a case, I would recommend changing it out for Perception. While Perception does fit a Priest (they need to be watchful for heresy), it is the least fitting of the Aptitudes, and I posit that Knowledge is more fitting than Perception.