They were talking about the Glyph of Seal of Vengeance. It gives you 10 expertise skill when SoV is up.
Expertise is not too important for a tankadin but 10 skill is nothing to be scoffed at, it's one of the best glyphs we have.
Second, would indeed be the RD glyph, since it's always nice not to screw up an encounter because your taunt failed.
The third one doesn't really matter actually, there's not really that many good ones to put there. Judgement only adds 10% and the ability is already pretty weak, AS ups your TPS a bit for single targets but you lose the flexibility, SA is almost useless as you should never have mana problems if you have BoS up. Other possibilities are Turn Undead (make it instant) or Exorcism (to be able to interrupt undead) but both are pretty weak as well.
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If it is weak, kill it before it gets stronger. If it is strong, weaken it.
