The attack is fine. If anything it could stand to go down. Death is capable of triggering a ridiculous number of death effects in a very short time. See DoSA for an example.
See Vulture for an example.
+1|0 per death should be valued at +2
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- +4
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(-1
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- +1
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after the -3 weapon cost reduction is accounted for)
Also remember this has to compete with Arsenic which automatically grows by +1|0 per turn.