pnp hellfire rays is far less op, as long as you got a sane gm who ain't gonna engage in purposeful obtuse and pretend as if hellfire rays do damage other than hellfire. hellfire does 50% o' its damage via mundane fire and 50% by means o' unholy energy. the original description for hellfire in the book of the damned splat book observes a protection from evil spell negates all the unholy damage. furthermore, unholy damage does zippo to evil beings.
so, hellfire rays, which curious enough do not have the fire descriptor and thus do not benefit from any fire enhancing spells/powhaz/abilities, only do half damage if you had forethought to cast protection from evil, a level 1 cleric spell... again, assuming hellfire rays use hellfire.
please note flame strike, and a few other spells, damage enemies via 1/2 elemental and 1/2 divine. unlike unholy, divine is one o' those rare untyped damages. is no good reason to assume hellfire rays does 1/2 damage via divine. converse, ordinary critical and construction has us reading hellfire and hellfire ray as doing same damages particular in the absence o' clear evidence to the contrary.
brief aside, 'cause am not particular interested and am thinking is no need for a right answer, but virtual all pathfinder spells which target souls fail against constructs, undead, elementals and outsiders. however, true resurrection is an exception. is a singular exception and even trap the soul, a level eight spell, fails when targeting outsiders. hellfire rays is a level six spell, so...
...
am such a nerd to remember this nonsense; am so embarrassed. nevertheless, while is not how wotr hellfire rays is implemented, according to the diabolist prestige class entry, when a diabloist converts elemental spells to hellfire, the rays gain the evil and lawful descriptor. would at least explain why you may target demons with hellfires and they do not shrug off the unholy portion o' the damage.
*groan*
can't believe we once again engaged full nerd mode.
HA! Good Fun!
ps with a level o' sorc, and perhaps one-to-three of loremaster, ember may be useful as something other than a spammer o' hellfire rays. "enter ye in at the strait gate: for wide is the gate, and broad is the way, that leadeth to destruction, and many there be which go in thereat." that said, ember is extreme useful as a blaster and is not difficult to build her as such. after all, wotr is a game.
obviously wotr ain't pro football, but is still a game.