Ah I love those heartattack moments in A1S when you just used swift for Shadowflare your coheal lags and dies to Spaser and you are right before prey + tankbuster... you can solo the double prey + buster if you have full Aetherflow and one tank uses his ultimate (especially Hallowed OP) but yea you prefer never to be in that situation :/

In general even as SCH heal > DPS there is no point in losing a raid because your coheal isn't that good, lags, is distracted, has a headache or other stuff just because you are supposed to DPS. Last weeks A1S our WHM lagged and after phase 1 I only managed 2 Shadowflare and a handful DoTs because had to make up for lacking AoE heals. My overall DPS was utter crap but we cleared and thats what matters in the end.