I targeted a skull piercer gnat while venerated rotpriest was in play , with audacity but no poison counter was generated . if the rotpreist isn't working properly like this for other people , please fix the issue . I'm hoping it was an isolated issue .

One think to watch out for: There's a difference between exile spells and exile effects.

To compare two of the exile cards commonly used in standard at the moment: Lay Down Arms is a sorcery. The spell targets a creature as it is cast. The spell Ossification is an enchantment. The target of the spell is a land. The enchantment creates an exile effect targeting your creature.

Rotpriest triggers off of spells targeting your creatures. So if opponent Ossifies your Rotpriest, that won't trigger the Rotpriest -- it wasn't targeted by a spell; only an effect

Opponents playing exile spells targeting Venerated Rotpriests do not trigger to give them poison counters.

In this last game, I had two Venerated Rotpriests on the board. Turn 6, Opponent played Borrowed Time, no effect triggered. I cast Gaea's Gift, effect triggered properly. Turn 8, Opponent played Vanish into Eternity. Again, no effect triggered from the Venerated Rotpriests.

Had either of these effects triggered, the Opponent would have received his 9th and 10th poison counters and lost the game.