For what it's worth, I took a strong dislike to AMR when it first came out - it was legitimately bad originally and I stand by my old position, at that time.
In addition to everything Kilee explained very well (better than I had ever given it thought) - AMR also came out around the time that both Icy-Veins, Noxxic, and another site I don't even remember anymore - began trying (and failing, horribly) to write guides for each class.
AMR got lumped into that nightmare of "Do Not Use!" websites - and the result of those sites was that the Spriest community on the Bnet forums, MMO-Champion, and Shadowpriest/H2P had to pick up the pieces - and undo a lot of the damage those sites programmed into people's heads: they would show up in our "Help me" threads, and state things like, "I'm doing exactly what _____ website told me to do, but my DPS is nothing like the other Spriests I see, and my guild just sat me!" - invariably the problem back then was that the information they originally found was detrimental.
At some point, AMR went through a massive change - particularly regarding Shadow - but I wasn't aware of it until one day I casually dismissed it as usual - and Zoopercat showed up here to inform me of just how different it was now, under her leadership. So there was a lagging effect where - for probably a year after AMR reno'd itself - it still bore a bad reputation (and I helped propagate that reputation).
It definitely doesn't deserve it anymore, and hasn't for awhile now. I have AMR bookmarked on my toolbar, I direct guildies to it all the time, when I meet Spriests who are turned off by SimC's complexity - I send them to AMR. This is the first expansion where I have run my Spriest through more AMR sims than SimC.
They made a fan out of me - and I was once one of their biggest detractors in the Shadowpriest community - so - I extend my sincere apologies for excommunicating something I have grown to very much like