Well the orbs floating around their heads are sorta insta cast (definitely not interruptible), and in RvR they will almost always use their un-interrupted casting ability...costs a buncha POW, but POW doesn't really matter much anymore anyway, so that's kinda moot.
When you see the swirly lights that look like the MoC animation...that means they're casting UI. When they stop casting like that for a second they are probably in the process of chugging a POW pot or /use 50% POW replenish ability, before they commence...
Yeah they basically get MoC for "free" and are almost always casting UI unless they don't feel they need to.
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