So would you prefer it be changed to something like 5hp per turn, to better play "chess" with? On a certain level, I agree with you, that in some ways you look at it and think, only 4hp? That seems pretty tiny compared to some of the attack values you can come up against. (I recently got wrecked by a double Courage team that ended up with with 60+ attack...) On the other hand, given the right kind of looping transform team, it adds up. When I said I don't depend on it for my team, perhaps I should have said rather that I don't rely on it to get me a win, since it inherently has no offensive value, but I do rely on it to keep Behemoth alive as long as possible.
Would I complain if the Immense trait got a buff? Of course not. Do I think it's necessary? Not exactly. I play him strategically, and his Impervious is just as valuable. I suppose, in that light, that you could make the argument that if it has roughly the same value in a team as a lesser trait, then it's not quite what you'd call a legendary trait. However, if Immense got a buff (say, 5 or even 6 hp per), then would we be getting calls for a nerf, since Impervious already adds a lot of value to the troop? "He can't be both Impervious AND gain a lot of hp, that's too powerful, not even true damage can keep up!" etc.