This is my shamans macro, and it does reset whenever i change targets.

/assist party1
/castsequence reset=target/combat Flame Shock, null
/castrandom Lava Burst, Lightning Bolt, Chain Lightning, Lava Burst

works great.

i've found that if you continually mash a macro, then the "reset=22" will not work, it'll keep going through the macro (and reset on its own if it hits the end) but it wont reset based on time if you're pushing it the whole 22+ seconds, i think its based on "22 seconds of non use it'll reset"

like my buff macro for my pally,

/castsequence reset=10 Blessing of Sanctuary, Blessing of Kings, Blessing of Wisdom, Blessing of Kings, Blessing of Wisdom

it wont reset if i push it once every few seconds (i pushed the button once every 5-6 seconds for 20+ seconds to buff everyone really slowly, just to test this theory) and it didn't reset back to sanctuary till i cast the last wisdom, unless i dont push it for 10 seconds, then it'll reset on its own.