Hey,
I play a lvl270 Chaplain, and honestly your dmg takes a deep dive after 200+ or so. For me this was no problem because I usually played this one with my friend.
As far as group play goes it is beneficial if u have Cleric2 for the heals. Otherwise its getting tricky in dungeon runs etc, not only because you lack heals but also because people tend to be more kamikaze as soon as they see something resembling a Cleric symbol.
As far as the Aspersion/ Sacrament/ Blessing discussion goes, I have Aspersion at 10 as well as Blessing 10, Sacrament got 1 Point, because most of the time thats the buff you gonna buy at the Pardoner Shops. I would say about 80% of players buy their Sacrament so their is no need to max that skill in any way and even if someone dies and you have to refresh it, the damage is not relevant its the extra hit. Same goes for Last Rites.
Aspersion even though maxed has a short duration when directly casted so no need to max it for buffing purpose, I maxed it for more dps but you have to remember its kind of a R2 Skill so the dmg will never be "high"
With the dps attribute of Aspersion at 60% I do around 2800 dmg, its not the world und it is kinda depressing when u autoattack a mob to death.
But yeah Chaplain is a support class so you have to roll with the damage dive after 200.
Blessing realy shines in Partysituations, I did some runs with a guy who had a 500 Blessing and everyone in the group hat 3 to 4 autoattack hits so min 1500 dmg more per hit is really good. Grouping up with swordsmen who have fast multihit skills really shows the dmg difference.