Looking For Multitudesagain, i must nit-pick the wording of this achievement. it explicitly states "finish" random heroic dungeons. according to blizzard an instance is "finished" only after the last boss is killed. so that means any partially or nearly finished pug groups won't count, unless someone from the PTR can provide evidence otherwise.
Use the Dungeon tool to finish random heroic dungeons until you have grouped with 100 random players total.
in an ideal situation, where each person you randomly are grouped with is new and different AND all the pugs you join using the dungeon tool are a success, a single person would need to run 25 pugs before receiving the pet. but when has anything ever been an ideal situation? lol.
i know i'm going to have to run more. the main tank of my guild is actually interested in getting the perky pug (now THAT'S rare), so instead of 25 groups, my total is looking more like 34. not including the possible fail runs and possible grouping with the same pugs over and over again.
this achievement looks like it's going to take a bit of work. or not. it all falls to RNG yet again. i'm crossing my fingers for an ideal situation... even though i'm not an idealist.