With new game play modes and GvG etc coming in, I hope devs shorten GW. The most time consuming and repetitive game mode for me even now, I dunno how I'll cope with it when all those new modes pop up....
I don't think GW is the real problem. I think the Pit takes way too long for average rewards and Ships is just poor. So many identical teams it's just an RNG-fest. It's a shallow, boring game mode that we know hasn't had particularly good take up.
But I fundamentally agree with your underlying point. Some old, time consuming content needs to be rethought or retired when this new game mode comes along.