the main problem with pvp right now is that strategy is not a thing, all you need is the right heroes and superior champion runes with 4th effects.
I've got an idea to force players to think 5 steps ahead
make pvp like campaigne. Add this system where players can add more rooms to their dungeons. And the rooms can be filled with minions(campaigne like mobs) that the player somehow obtains. The minions will have to be strong enough to cause a treat, and force players to bring a healer and use abilities, but not too strong so that it's like 4 heroes vs 20 heroes. and speed will also be a matter, as kobal can just wipe out wave after wave. The devs should also add theme rooms other than just Crypt, like Light Forest, or Fire, and diffrent themes boosts and supports diffrent minions. Boss Island dungeons minion strength should be good for a level 70 with 6 star fully ascended, blessed, stocked with champion runes heroes. The higher level, or league, or whatever, the more minions and rooms you should have, and to make it fair, you should be able to carry 5 heroes, compared to the final boss of the dungeon-the opponents 4 heroes
Something like this will cause heroes to use a key ability to prevent anihlition, and make 2nd and 3rd abilities availible, and cause cooldown being a key thing. The only down thing is that this will cause alot of testing, buffing, making new minions(you can get them from campaigne), and nerfing related things to make sure there's balance. and we all know that the devs don't like doing that kind of things.(But this is also a chance for the devs to get more money, and to make gems important again)
The Great Monk- Key shall protect my dungeon from attacks