There are obviously better choices for healers, but s/p is nice soloing class as well, and can be fun to play

And that's what matters most.
Is it viable? Absolutely! Thought it may not do the best heals, it does competent heals, while also able to supply the party wide a decent boost in DPS. Much more so in long fights...
Spiritual Leader is a great support skill, however iirc, doesn't stack with strong stim, so would have to be used after 30 seconds into the fight.
You shot can also increase the pcrit and mcrit of your party members, not much, but if they aren't over buffing it helps.
And the 70 elite being your most useful support skill during a burn. This skill increases your aggro leaders damage by 10% which is considerable if your tank happens to be a wd/w. Also helps in cases were your tank might be having trouble holding aggro. S/p Helps them quite considerably with incoming damage reductions, and outgoing damage increase.
There is much better dps, there are certainly better heals, and well, there are better support classes :p But yes, I can still see this being viable as a healer in endgame, with the ability to also utilize it's support abilities.