It is possible that just way more people are actually trying this for the same reason. I myself have 10/250, some day I will have 250/250 and will never get to 251. I probably tried 25 matches to get those 10, with 2 given to me by forfeit. So if you go up against a guy who looks like he has no idea what he is doing, it's probably me.
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I actually don't like the PVP aspect. Been dreading this achievement, so the longer it took 5.3 to come out was fine with me. I don't like that I have to do this to get the pet. I honestly don't like any PVP, and pets/mounts/achievements that require making us do PVP is not fun for us that don't PVP. For those that do PVP hate us for trying because they are stuck with "idiots" who "suck" at PVP.
For pet vs pet though I would imagine those that are skilled at knowing all the ins and outs they probably love us because it's an easy win for them.
/* steps down from the soapbox