My first ritualist

I tend to find the Channeling line has more oomph to it than Communing, in general.

Also, a single Shaman's insignia isn't going to do you much good. The armor bonus applies only to the piece of armor equipped with the insignia ... not the whole thing. In my opinion, you'd be using up insignia slots better suited for extra health. Besides, use your spirits right and you're not going to need extra armor. Well, by that logic you won't need the extra health either. I think the extra armor is preferable because the scariest stuff in HM are things like Elementalist bosses, who put out bursts of armor-sensitive damage.

Now, that's a very debatable point for most classes, but for a spirit spammer, you're less likely to be focused on by melee monsters, who target your spirits. The likelier scenario is being tagged by an AoE spell targeted on someone nearby. In that example, you can't even fall back on Prot Spirit, because you were just collateral damage. But then again, that's just my experience.

I will however, admit that Shaman's Insignias are really expensive at the moment. I'd use cheap +armor ones until you can either afford them, or find them yourself.