Why do you think so? If you're in cleric stance for the majority of the fight MP will not be an issue. If MP isn't an issue why should you use physick? It's like you're telling me to use ruin over broil because it's more MP efficient.
With 12000 MP:
If you only broil for 60 seconds: 530 MP x 24 casts = 12720 MP
40% natural regen in 60 seconds + 20% from aetherflow
884 from energy drain x3 = 2652 MP
Total MP regen per minute = 9852
Your net MP loss per minute is 2868 with broil only. Using dots will reduce this further.
bio II = broil MP (no difference)
at least 3x bio -> (530-353)x3 = 531 MP saved per minute
at least 2x miasma -> (530-442)x3 = 176 MP saved per minute
at least 3x aero -> (530-353)x2 = 531 MP saved per minute
2 shadowflare -> (530-707)x2 = 354 more MP used per minute
net total is 884 MP saved per minute
so per minute you lose about 1984 MP. This will last you around 6 minutes of nonstop DPS (slightly longer because you start with 3 stacks). Most fights have downtime so you will use even less MP.
If you are sustained healing you should use physick. But forcing two healers to sustain heal is very rare. You can think of it as losing about 1 DPS each time you heal. Using high potency spells will reduce the frequency of you healing and therefore increase your damage output.
