As a bard I can confirm the effect of rune spells on aggro. I have tanked several times for rag-tag groups with no one else to absorb the hits. All you have to do is spam the level 49 Shield of Songs a few times to get initial aggro and then keep it in your twist to cover the casters' aggro.
That is because you are buffing rune on the whole group which makes the mob angry. Try being solo sitting next to a group and rune yourself, 0 aggro. Same with this axe, the rune proc does not generate any aggro because it is you buffing you, not you buffing someone with aggro.