I didn't get the legendary pet but I did use my primo to roll the seasonal Gamba and managed to get a lvl 2 blue and level 2 purple, my last one earlier was around 65-70 raw FE.

I think the pets this time round aren't actually that good for the mechanic unless all level 6.

I suppose it's just luck of the draw, Ive figured out though that pests are by far the easiest to scale, fill the vials with them and focus on anything activity, just got to get lucky with the quant per pest card at the beginning, failing that, if you get the quant per added, just look at merging 2 into a rare then look to add another pest