This damage isn't affect by Weakness or Resistance
Energy Trans shuttles Grass Energy freely between your Pokmon, which made it an engine piece rather than a beater, and Pollen Hazard stacks Poisoned, Burned, and Confused on the Defending Pokmon for just 20 damage
Life gain has been a necessity in mono-black to keep up with its own demands
Getting to put a land into play right when you hit it with Explore is super relevant in the early game, and while it drops off some late, it certainly doesnt hurt
Skrelv, Defector Mite has a similar effect while also being a legendary artifact creature for all the possible synergies out there
That's a lot of utility, all wrapped up in one super-economical 4-mana package