Rift is more successful in stunning. The range is big and less than half a second to cast.
You can't expect skills to keep getting stronger. Weren't you the one who is annoyed that people can constantly KO monsters and bosses. Rift is use for PvP and not to outmatch celestial.
Their logic is that soul master are suppose to be weaker than priests I guess, but oh wells. Priest didn't really get any stronger AoE this time so can't complain :P
Yes it cost way too much MP but have you seen elemental boost? Lv1 it cost 1K mp and takes 2min to cool down. I'm pretty sure all new skills cost a lot of mp.