Murky vs Ragnaros
Ragnaros is very difficult for Murky to lane against. All three of his abilities hit hard and he can easily kill Murky and his pufferfish. Murky will have to use his pufferfish as bait and then kill the minion waves with slime. If Ragnaros does not stagger his abilities Murky can get some slimes on Ragnaros and force him to retreat.
Fish Tank will help a little with Ragnaros. But Murky still has the two other abilities he must dodge or bubble out of. There are probably easier targets to go after.