As in terms of the sigil, for tank healing in a raid, the greaters Hailstone Tideshard and Frozen Deep One Tear stack with each other and provide larger shields on the tank then just adding straight spell power to your sigil would. The 564 shield from the Hailstone Tideshard procs ~20-10% of the time, on every heal. With an assumption of 10% proc, that means a 56.4dmg shield from every heal, for that value to me equated to Ancestral flame you would need a 94SP from a lesser to make it worth getting. From Dark Rituals one of your BiS lessers, only equates to 36SP and 20SC. Even though I am ignoring the SP/SC bonus your actual heals receive, if you do the math they turn out to be better.
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