The Hydrochloric Acid node says “You have a chance to poison enemies while standing in your Poison Pools.”, but what actually happens is that you only need to walk through your poison pools once and you get the buff outside the pools too until the pools last
2021-08-06_23-40-09.mp4 here is a video of the bug too cuz seeing it is easier
I believe this is just a confusion over how the node is written more than actually a bug. You will notice that even when you stand in the pool and it dissipates you will get the buff for 4 seconds. It is inline with for how long Poison Pools lasts on a target; it poisons targets and also puts a positive buff on you. That means if it disappears or you step out of it you still will have it up until timer runs out.
I made a note of how this can be confusing. Thanks for the report.