Naw, if anything we'd use Trick shot rather than Piercing. Piercing simply drains *far* too much focus to be used for anything but burst-AOE in dungeons reliably as far as I can tell; Remember, your regeneration gets smashed with arcane shot over sidewinders.
This log:
https://www.warcraftlogs.com/reports...pe=damage-done
Has even better success with trick shot, BUT, I think there's something funky going on - if you go to Datarro's aimed shot, you can see that unlike mine which has the exact same cast and hit damage (
https://www.warcraftlogs.com/reports...ability=-19434 589K), his is set at wildly different amounts (
https://www.warcraftlogs.com/reports...ability=-19434 907K cast, 621K hit). Clicking in further, you see odd stuff like this happening:
https://gyazo.com/1806d51ec96ee23b14c005546eef9e91
(yes, that's two aimed shots hitting in the exact same milisecond, one for 519K and the other for 1.4M crit). It happens MULTIPLE times through the fight, again at 13.942 and to his trick-shot aimed shot at 15.043).
So if we assume that his average hit at 621K is the real damage, rather than average cast at 907K (and 621K lines up far better with my own results - add another 15% to some aimed shots because of trick shot hitting no extra targets, and his legendary belt buffing it a bit, and the numbers are close enough that we can assume this to be true), it means his aimed shot did 56.5M down from 82.6M, and this would drop him to 121.5M damage, or about 392K dps (which is lower than a fair few sidewinder-logs that I've seen, my own included).
TL;DR - Piercing shot seems excessively expensive with no big focus generator. Only other competitive log that doesn't use sidewinders so far seems to be bugged (evidence above).