RMs, the ultimate buffers/ressers, but what do you need in order to become one?
1. A lot of patience, you're not going to party with the greatest people all the time, and you are not the greatest soloer of all times (Blades take the cake on that one :P)
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Yeah. Rori is good for AFK spamming, but after that I'd use the Guardian. Chances are that +15% HP will save you more than once.

Rori's good for general buffing as well, it reduces the cost of the buffs. And yes Guardian may help you survive, but Merkaba depends on your stick's melee damage rate, so all in-all it's better to get the Angel Stick, even though it gives a lower HP bonus, the higher damage will make up for it.

And also Angel gives more INT than Guardian (iirc), then again it's all up to your playing style, I'd like to survive as much as the next RM, but I'd also like my partner to have buffs for as long as possible. But again, that's just me.