Ok lets just freeze the argument until today's raid
My points so far:
Smiting is weak enough to be called healing and the strength of the spell fall in the category of support healing , it and should be used when its safe to do so aka you dont expect anyone to take significant or lethal damage that you wont be able to counter with your smite.
Raids will be hard , one way or the another disc will find himself outclassed on some encounters and good on others , when the raid pressure is significant and can lead to deaths , i doubt disc will manage to handle this but in some encounters where the damage is focused ont he tanks and the mechanics are somehow strong but they dont really push the groups to the edge , disc will probably be the best to choose but thats only because the supportive healing it does is enough to keep his group alive , there will be aot of raids with interupts , movement etc , disc wont have easy time to setup everything and nuke.
Everyone's else points:
Smiting is strong enough to be called healing , well iguess we have a problem with names and perception about what is strong or not
Disc does most and lot of dps with instants - pretty decent argument
Its rare for a raid group to take too much pressure that will lead to deaths in a short time period - this depends entirely on the boss
Mass attonement plus damage is a reliable t hing - i personally think that it wont be so easy
The biggest problem with disc is how often he realize all these perfect scenarios where he set everything up and do his job , we gotta have the raids first to see this.