Murky vs Kaelthas
Murky can certainly lane against Keal'thas. Save your bubble for when Kael'thas lays an ignite on you if possible. Be aware that one of Kael'thas first talents is for a quest for flamestrike.
Kael'thas greatest weapon is his stun. It is also his only escape. Slippery When Wet will let you run down fleeing Kael'thas for that final hit or two kill him.