Even Tiny Twister or Tiny Bog Beast arent worth stoning, place an alt each place (or fly, close together) and reset the batch each day. Just like a daily task of 15min and you will find the rare in your prefered breed. Theres not many breeds available to them so thats quite easy. Flayer Youngling is another specific area spawn but 10 breeds available, Ive found HH, PS, HP and all subbreeds, yet SS or PP so I stoned one. It was not because it was hard to find any up, plenty nodes, same as Bog Beast and Twister.
You want to stone rare pets in the sense of not many nodes up and/or many breeds (if u even care about that). Also some pets dont come as secondary or tertiary pets even while in same zone, that could option in aswell.
Wildhammer Gryphon, one could get lucky getting as secondary but primary abit meh. Save for last when rest of pets in zone are done.
Larva ghostlands havent seen more than 2 spots, however single breed would make farming rare okay if u get onto a realm with them up.
lofty libram, had no issues. Irradiated roach realmjump that one. Winter/summer pets are up for 3months? Very busy farmers first few weeks but then they tend to spawn quite ok.
Im having trouble with Redridge Rat but thats because 80% of the zone phasing issue, can be worked around with a fresh toon who hasnt quested there yet, little project i gotta do, my main has cleared all quests.
Scorpling does have only a few spawnnodes, dunno if it comes secondary but 3 breeds only where 2/3 would be acceptable, lucky cointoss like Bog Beast and thats done. Skittering Cavern Crawler same deal.
It really comes down to each petcollector themselves what they are struggling with and if you do have spare stones which you usually end up with of: humanoid, undead, dragonkin, elemental, aquatic etc sure stone the last few if they are just collecting dust, time saved is time earned or smt
But I would never stone a wild pet like MacFrog that comes in abundance and as 2nd/3rd pets, that I'm too stubborn to do.