Magic int on DW poison

Was fighting gargs, hadnt cursed before or after yet you can see from the photo

probably hit before the gargs had time to spell up that's my experience anyway

I've had this happen on my warrior as well.

Does normal poison give this message.
Without checking the code, the logic should be similar if not the same.

Unsure, haven't tested on my sorc yet. Pretty sure I didnt see any spells being activated

It would appear that the message is a standard part of the poison spell and is issued if the target is already poisoned by a more powerful version of the same spell.

I would suggest that Yatana's explanation is quite plausible as your spell's power is modified downwards by Harden and Immunity. The gargs do not have Harden but they do have Immunity and the Immunity increases after they spell themselves.