This may sound odd, but I have began to feel a bit sorry for Unborn Valk'yr and Murkalot habitual users. While this may sound pretty lame, hear me out.
It seems that these two pets above all others cause severe stagnation for the user. Each pet seems to become something of an anchor/crutch to the player, especially with Murk. In the case of Murk, it seems that every single time that I see him, he is paired with a Fossilized Hatchling, and often Kovok in the third slot (though I do run into one player who always uses a Mechanical Pandaren Hatchling in the third slot almost solely for the Decoy). Without a Nether Gate or one round stun (i.e. Crystal Prison) used on your very first turn, you are going to get hit with the Murk player's RI boosted Bonestorm every time. The point being, the Murk user is ALWAYS paired with a strong AoE type pet, without fail. In the last three weeks, I have yet to see a Murk opener without an RI into an AoE, where an RI boosted high dmg single-target type attack would literally one-shot a pet without Deflection, and would come out first to boot, resulting in zero retaliation dmg. Of course, the AoE total dmg may be more advantageous, but then again, 3-2 pets is not exactly bad either. To me, it seems that this dependence on one pet dictating your team's makeup is ultimately self-defeating, at least when it comes to enjoyment of different pet compositions and strategy.
Valk users are a bit more varied, though far too often front-loaded to take advantage of the broken Haunt mechanic. Valks paired with Blighthawks or Stitched Pups are pretty much the norm, and seeing them teamed with something more strategic is fairly rare. For example, a Haunt boosted with something like Acidic Goo would be very effective, but I have yet to see it. Valk usage also becomes extremely predictable as well. Unskilled Valk players simply rely on casting Doom on round one, and Haunt on round two (even worse players simply use Haunt on the first turn), and behavior like this is easily juked. If Haunt ever received a CD (like it desperately needs), then players like this would have to abandon it in favor of something easier. Skilled Valk users can wreak Havoc on a team by anticipating jukes and using Haunt to avoid dmg intentionally (for instance, in waiting one extra round before casting Haunt to dodge traps about to go off or the like). As for other spells, I do not recall ever being hit with an UA by a Valk in pvp, and this is a very potent move. Once again, this locks the user into using only one pet/spell type, which to me seems pretty boring.
I know that people like to win and I am not taking away from that, but to me, half the fun of pet battling is constantly tweaking comps and trying out different ideas. I find it rather constraining to think that I can only consistently win with one comp. By the way, this isn't an "OMG THAT PET IS TOO OP" type of thread, just observations that I have made. I would like to hear from frequent Murk and Valk users about their thoughts on this as well.