IMO the root of the meta-misery is in the similarity of defense teams. This can be avoided if the defense teams can be assembled only from a limited set.
I suggest:
- be 10 defense-team slots, separate from the attacking team slots
- 6 defense-teem slots be marked with the 6 mana colors, because the system picks these automatically for the appropriate day of GW to defense
- the remaining 4 slots will be the PVP defense, from which the RNG choses one, when you’re picked for opponent
- all the 10 slots must fill up from the same troop-pool, where every card have only 4 copies max (or less), if the player has so much in his possession
- so, if you make a Kerb-G.Spider-FG-Kerb team, you’ll have only 2 Kerberos for the remaining 9 team-slots, but a Psion-3×Famine team you can build only one times
I think, this system provides opportunity to use meta-teams hereafter, but at the same time forces the players to set up more diverse teams to defend. Furthermore, it solves the problem of daily defense teams of GW, because players do not need to look at and set up daily defensive teams each Monday. And, of course, the random 4 PVP defenses give some diversity, when the system offers for you the same opponent again and again.