Just simply a sub-optimal build, cultivation easily outperforms SotF in 5-mans, your are either geared wrong or just failing for other reasons.
The fact you think WG+SotF outperforms cultivation on group AOE (much less without prosperity...), in comparison to a mastery build where you will have 3-5 HoT stacks on all players (5-7 on-tanks), is just odd. Cultivation essentially doubles your rejuv healing (slightly less, though with the extra mastery stacks it evens up)
continuously during any AOE mechanic, with no CD, and adds another free mastery stack for all spot healing. And cultivation only requires someone to dip to 60% to reset the duration, in reality this happens far more than people think for a player that even looks "OK" at 80-100%, dipping to 60% and back up happens often in the 6 second duration when many mechanics hit for 30-40%+.
And the mechanic you noted don't even make sense in that context... For instance Scorps are purely a throughput mechanic, not a one-shot mechanic. If we were talking Arcway or the last boss of BRH, OK, but that becomes a binary issue of group comp, mitigation, and mainly chain stuns (including pounces). You don't heal through one-shots, you stun, mitigate, or CC. Whenever throughput is needed, cultivation is the clear winner.
The only 15+ clears so far used cultivation for a reason.....