Okay. So yes and no. Nightcap and Oak each have their counters. Super Brainz and/or just squad of zombies will beat both.
Now, I have been talking about a mode similar to Overwatch's ranked mode. Not the ranked part, but the class choosing bit. PvZ just added Offense, Defense, and Support classes. If they added a mode where you choose your class ahead of time, and go into that mode with you roles assigned, I think that would fix it. Now, that would be a mode for people like you, waiting for the hype to dye down over those two plants, but Giddy and Turf Takeover and all modes in general should keep this out and just let it be it's own separate thing.