Update: In collaboration with my guild and inspired by Seonsu’s original post, some testing was done to determine exactly whether imp weapon totems actually improves the AP of the group.
Short answer: Almost surely no. Shamans who are imp totems should respec immediately.
Long answer: We went to Blasted Lands to hit mobs for 10 minutes. We ran a group consisting of 2 warriors, 1 rogue, and 2 shamans, one with imp totems and one without. We first let the shaman with imp totem talent drop WF, and then we proceeded to hit the mob for 10 minutes. We then let the shaman without imp totems drop his WF and then hit the mob for 10 minutes again.
If the AP buff was applied, then we would expect a clear difference in top end damage as a result of the bonus AP of the WF totem. This was not the case. This is actually most clear in Veezi and Freedrakeo’s max damage. (The extra variance in top end damage for the two warriors is most likely the result of Crusader proc. Veezi and Freedrakeo did not have Crusader on their weapon.)
The lack of difference in top end damage gives good evidence that the AP bonus from the talent is not actually conferred onto the group. Thus the character panel is correct when it shows only a 315 AP gain from WF proc. Interestingly though, as Seonsu mentioned earlier, the shaman with 2/2 imp totems does actually see a boost of 409 AP on their character panel. From our testing this boost occurs as long as they have talents in improved totems regardless of whether they are the ones to drop windfury or not. That is why Freedrakeo’s top end damage is the same in both trials. This is corroborated by looking at the shaman’s AP in the character panel.
2/2 Improved Totems top end damage: https://imgur.com/a/yKkQgv0
0/2 Improved Totems top end damage: https://imgur.com/a/nBRm5lx
If anyone else cares to test and see if they can replicate, then please post your own findings below.