For the record I don't agree with the gearing in those guides. I guess the differences aren't big, so really a Sage just has to figure out what they like best. For me, or in my opinion, It's good to have about 30% crit after all buffs and stim, which is just shy of 300 crit rating. I have surge to around 450, which is soft cap and the the rest into alacrity. It's a very well rounded stat distribution that I feel is best for healing performance despite what any spreadsheet say is the best healing per second or healing per cast time.
I won't deny, I do have crit in my gear, it helps me to force regen when I can. But not derailing into a crit vs power/surge vs alacrity discussion, the guide is just a guide. Healers don't have a set optimal rotation like DPS, but more on what is needed and gear is the same, in time you will know what works best for your healing style, and healing role (group or tank or mixed) healer.