Environments were released in Galactic Gardens as a new game mechanic and card type. You play them in a ground lane and they have an effect within that lane until they get removed, either by being replaced by another environment, being bounced by excavator, or by being planet of the grapes and getting eaten by squirrels. Given that only one of those three things is general enough to do for most decks (and is the only one plant players have access to) most people end up running some environments in their deck to counter opposing ones. However, this brings up an important question:
Why run environments in the first place?
Some environments are just good enough to run on their own as straight up good cards in some decks. Spikeweed Sector, Bog of Enlightenment, Area 22, Hunting Grounds, Black Hole, and Moon Base Z (you can make an argument for some other ones like Laser Base in specific decks, but these are the ones that I use on a semi-regular basis). These are cards that you'd run even under the assumption that under no circumstances would you ever run into another person playing an environment. They are unquestionably worth running, and my argument is that they're the only ones you should be running.
Let's assume you're, for whatever reason, running Coffee Grounds. Maybe you're playing Captain Combustible midrange because it's the least bad environment he has, and you have it simply because you're worried your opponent might play an environment. If your opponent never plays an environment, it's 100% useless. It doesn't advance your likely midrange gameplan whatsoever because it doesn't help trade (in 99% of scenarios) and doesn't provide new board presence. You'd rather have a different card that does advance your gameplan. If your opponent does play an environment, now you can replace it if you have it. This still runs into problems however, one of which being your opponent is zombies and as such has already received an advantage off their environment. Your best outcome is stopping it from doing anything further for no actual advantage afterward because as we already established, this card doesn't actually help you. The second and more pressing problem is that it forces you off curve. You're diverting your gameplan off of creating board presence to just stop your opponent from getting more value off something he already got most of the value off of from the surprise factor. That is also bad, and you're still better off having a different card and just playing around the environment normally. This argument extends for any plant environment that you're playing that isn't worth running strictly due to it being a good card for your deck.
Then, for Zombies, it's a very simple argument. You have the same problems with diverting your gameplan that plants have, except you can stop the environment from ever getting value because you play last and can cover it immediately. Now the second problem is that plants mostly don't have anything worth dealing with. Their environments suck other than spikeweed sector and bog, and while those are good cards they aren't must removes and aren't prevalent relative to the overall field of decks. As zombies, you don't have a reason to run environments strictly to counter because you're not going to run into environments to counter in the first place, and even if you did, you'd still be diverting your gameplan, which you don't want to do because it's worse than just playing to your plan.
In conclusion, environments are just like any other card: you run it when it's the best pick for the slot and works towards what your deck is trying to do. You figure out if you want the card even against people who don't have environments, and if you do, then you run it.
I think three of an environment you like is a good rule of thumb. IMO environments are slightly more useful (and slightly more of them are useful) than you make them out to be... however, I have seen decks with no business doing so running six environments, virtually guaranteeing they’re going to end up with a dead card at some point in the game. This is obviously overkill. No deck should ever run six environments.
Unless it should.
But, yeah. Basically there are two ways of winning. You can win by winning the environment game... or you can win by not playing it at all.
Same is true for gravestones. You don’t want to be forced to play your only Stone zombie late game V. Guardian, because it’s going to get ate. Better are 20 gravestone zombies or 0.
The main point is that you shouldn't run environments simply for the sake of it, because that does more harm than help. You should be running them because they do something for your deck that works with your gameplan and does so better than your other card options. You can definitely argue that for some specific decks there's more environments than I just listed that are useful, I mostly only listed the ones that are more general (and I guess bog, but bog is really good right now). Graveyard and Laser Base are the kind of borderline stuff that you can definitely find good applications for, such as in the deck you provided.
And yeah, very few decks have any buisness running more than one type of environment. The vast majority don't have two that are worth justifying in general, and overlapping them just causes even more problems.
My Imp deck is virtually guaranteed to win the Environment Game. So if you want to win the Game, you might be better off not playing them. (Thus it is both point and counterpoint to your argument.)
Zero environments is viable with any hero that doesn’t have three environment superpowers and access to Excavator Zombie.
Do we agree?
No, I think it's all point to my argument. Your deck runs envrionments because they fit with your plan, which I fully support. In turn, even though you have environments, running strictly to counter them is a poor idea, which I also support.
Zero environments is definitely viable on anyone who isn't HG, yes. HG is kinda forced into it a bit since he has his supers, which means he wants excavator, which means he wants some other environments too. It fits right into his gameplan. Nobody else has that kind of dynamic. That being said you still don't have to go 0, you just need to remember it's an option if you have better cards to run.