To draw from Magic (I know, I know some don't want elements to be like Magic)
Magic is very successful at having deep defined colors however it doesn't do this by keeping skills sequestered in each color/element. Rather it has some skills that remain exclusive to their colors and other skills are spread to additional colors as appropriate. In Magic is is not the skills that define a color but rather the color defines which skills will be present and in what quantity.
Life has both defensive and offensive poison (Thorn Carapace and Forest Scorpion)
Death has both defensive and offensive poison (Plague and Deathwalker)
I would suspect that a Life & Death creature would be allowed to have poison appropriate to both elements. now this card does indeed draw more from death than it does life but that is appropriate after all this card does costs more

than it does

.
Now about death and healing
Life currently has 3 skill focuses [Player Healing, Efficient Creatures, Poison]
Death currently has 2 skill focuses [Poison, Death Trigger]
So it deserves another. (maybe recurring without a grave?)
Water currently has 3 skill focuses [Freezing, Utility (lots of cross element abilities), Player Healing]
Light currently has 3 skill focuses [Quanta Generation, Creature Healing, Player Healing]