to be honest; I think they should rework deadly altogether or offer an alternative effect of simliar but slightly lower value. Deadly is just hard to balance because it´s so unconditionally powerful.
my proposal would be a withering effect that doesn´t do dmg to the zombies power but assignes it as -x/-x to the plant. which would be very strong but more predictable, easier to balance and in the end; you can slap it on more cards without regret
to be fair; all classes have weaknesses if you look at them alone.
