why isn't there different terrian for online battles?

Welcome to the forum my friend, and worry not, this topic has not beet covered before. (At least not that I remember).

I think that the map is fine as it is right now.

I mean, for advanced players I think it would not make a big deal, but it will for new players, specially when there are decks that would benefit a LOT of having 2 water lanes, while many others will suffer their lack of amphibious cards.

However, you still can find these special maps on the campaing mode. (Story mode, or plant/zombie missions, however you want to call it). There are maps in there that are as you said, with many height lanes, with many water lanes, or without both of them. (Besides the normal map, of course).

But who knows, maybe one day this feature will be implemented.

I do think its bad idear in general because it is a randomized factor that can overthrow one players gameplan without any interaction of decks. 

In my opinion it is one of the worst misconceptions in Gamedesign that has grown quite big lately that randomness can improve a competetive environment. 

Sure, it allows for those moments where streamers can scream like monkeys and throw their fecees at the wall over how lucky they or their opponents are, but RNG shouldn´t participate to much in the outcome of a game. Consistency is much better.
While you cannot eliminate RNG completely from a CCG it shouldn´t be dominated by it.

>it´s always hogger

 @wonoz My thoughts exactly.

While I appreciate the desire to make the game more interesting, I agree with the other posters that this is one aspect that should remain as is for League battles.  I wouldn't mind there being a different battle set where we could agree that lanes would not be standard, along with other rules, much like the offline Missions.

BPRD