A new game mode wont fix the fundamental problems of league of nerfmaster sucktown. Defense items are too powerful for their costs, combined with tanks farming too well, as well as the overabundance of CC with no diminishing returns leads to the league of tankydps steamrolling everything, with only a few outliers who don't fit that who are "viable."
Also the lack of "core features" is going to continue hurting the game. No replays, no mac client, no spectators, magma core delayed and delayed and delayed. The new champ every 2 weeks release cycle apparently really hurts the development of other features, no matter what the devs protest otherwise. or maybe its just their new chinese overlords, since tencent just gave them quite a large stack of cash a couple months ago.