Well, that is pretty much how Amanitar acts when I fight him. Of course, that's true of most bosses, so it's something we ignore. In this case though, you've presented your position of how Amanitar would fight. I'm seeing some flaws in that, as well as a lack of consideration for Eck, so I'm saying how I disagree. Try not to make too much of what you think I'm not saying though. I may just see no reason to say what you've already said.

But if you wish me to explicitly concur that Amanitar could try to use those tactics, fine. He could, those would be wise things for the boss to try. Against some bosses, that might even spell inevitable victory. But Eck can use his own abilities to counter those of Amanitar. Jump out of the roots, close the distance to Amanitar. Vomit over nearby mushrooms, clear out the bad, get the buff from the good. Really, if you assume Amanitar can think of an ideal strategy to use against Eck, then why can't Eck think of a counter-strategy to use against Amanitar? Dumbness? But you've said they're both short on brains. So either put them on the same field, and don't try to make it some fancy strategic game, or give them the same advantage of strategy.

And no, nothing bad happens when you destroy the poisonous mushrooms, so that means nothing. And given that Eck is apparently able to produce quite a copious amount of rather powerful digestive acids, I don't think it's reasonable to assume he'd risk organ failure from biting the mushrooms either. Even if so, that'd be days later if not weeks. Which might make for a satisfying victory in its way, but outside the scope of the discussion. So at the worst, Eck gets some healthy mushrooms in his AOE but is too far away to get their buff. Fine, but he can jump to others around him if he gets mini'd. This also invalidates any particular bad luck when it comes to mushroom spawns, since he can jump to a safe location.

Sorry, but I just don't see your reasoning as persuasive, and also, I think you've missed a vital point about these discussions. The bosses are given a rough parity, so it doesn't matter whether it's Eck, Illidan or Van Cleef duking it out, at least in terms of power. In terms of their specific abilities, well, that is what matters, though in some cases we may need to make allowances. The trick is to keep them roughly equal.

In this case, I just don't see you being fair to Eck.

Oh, and I don't know about you, but I've done just fine in the fights without caring much about the mushrooms at all. I don't think I've ever deliberately killed a healthy mushroom.