Just wanted to echo this bug/behavior with my experience.
For my ranger, the Wounding Shot description read: "Deals 20% weapon damage per 3.0 sec for 9.1 sec."
In my test, Wounding Shot did 31 weapon damage initially, followed by 4 ticks of 2 damage, and 1 tick of 0 damage, for a total of 8 damage over time.
It seems like the first tick of damage happens immediately after the ability lands, rather than starting at the 3.0 second mark. Also, clearly, the damage per tick is less than 20%, which makes it rather lackluster and disappointing.
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