I think this is wishful thinking.
==Guinevere gets tankier==
8/8 5* 4.80 Guinevere to 5*+17 Defense/ HP build goes from Defense 778 to Defense 899 and HP 1347 to 1527. Luckily for attackers, her Heal Over Time does not scale with her HP.
Most talents have such a low proc rate, they only really change the hero on war defense teams. War attackers can skip your defense, but not re-roll you thanks to revive timers. Thus a good war defense team can lock up war points if no one wants to attack it. Even if you are correct, and Guinevere is dethroned for war defense, I see her staying viable for raid defense.
None of the anti-Guinevere heroes have really caught on because they are niche.
If the Devs introduce and anti-talent hero, Guinevere having a poor class actually works in favor of spending Emblems to boost her Defense and HP.
==Hel and Guinevere ( together they fight crime )==
Hel is popular, but players could split emblems between Hel and Guinevere given the way Emblems scale Defense on a 5* talent grid.
MY PERSONAL OPINION
I do see more players without a good center hero experimenting with some of the defensive classes to see which of their heroes is the most annoying.
With partial Emblem reset for gems and full reset for tokens, people are going to play it safe, not try quirky builds. I expect to see a lot of Alberich, Mother North, Guinevere, Delilah, etc. go the straight Defense/ HP build for 5*+17. You can see HP’s effect. Defense scales non-linear. You can see the impact of this talent grid with Titan stats. While balancing Attack, and mana gain, are trickier calculations. Unlike Pokemon GO, you cannot predict which Titans, or war opponent, you will be fighting so going the safe route will make sense for even more people. I hope after the 6 month data mine reveals copy, after copy, after copy, of heroes, the Devs will reconsider respec costs.
==Gravemaker==