As several posters have already said just go stand next to Muradin when you jump over so that you have proximity agro over the melee. When you first jump he doesn't do much damage without any damage stacks on so you can easily stand next to him until he finishes evade bugging out then he'll agro you from proximity and you walk him back to the edge in range of your healers. The reason your melee are dying after an "evade" is because of proximity, they are closer to him and get one-shot before you can land another agro ability to pull him onto you. If you go next to him until he follows you, that's not a risk and should never happen.
Secondly, if you jump back over too quickly as a tank he can turn on the dps still on the boat and kill them or switch targets and throw an axe on other players. Assuming your dps isn't taking way too long, you can easily afford to stay there and tank him an extra few seconds while everyone jumps over before you that way no one dies on the boat or gets hit by the axe after you jump back over.