I haven’t got her fully levelled let alone emblemed (just pulled her a week ago) but here is my take on her:
Mana cut to all is always helpful. Even with all these new heroes I still keep a weary eye on older heroes like Li Xiu and Neith when I run into them because they have ruined many a battle for me.
*She can create a nice synergy if you have other mana controllers, be it Hel, Li Xiu, Neith, Proteus, etc.
I would argue that there are only 3 Holy Heroes who would be better tanks than Guin; Zuri, Lidenbrock (sp?), and Wolfgang. What this means is that Guin is still very much viable in that role, so in those tournaments that have no Dark element she will excel, but even in war or normal defense she is a great option for tank.
I’ve always wanted to have her, she’s one of my favorite heroes. It was an ongoing joke in my old alliance that I’d give my left titty to pull her (the bigger one).
Was pulling during Challenge festival, but no such luck.
Now, I am not as active as I used to be, I am still lurking around though, but I might not be all up to date with all the newly released powerful heroes.
However, after getting Guinevere from HA10, it didn´t take me long to consider spending all my ressources on spoiling her. Facing a tank that has mana cut can really turn the tide. And a yellow one too, even.
I do not know about you, but my Dark heroes are so terrible - so few Dark Heroes out there that are Fast too. So I fear yellow tanks the most!
I´m F2P, which probably also plays a large factor - but even if I was not - gosh, imagine the ‘luck’ one would have to ‘buy’ to land a better yellow tank?
Here is my Guinevere in the strongest possible version - and I use her for everything (she replaced Li Xiu in my Yellow mono team (I still just have a few Yellow five stars)
F2P, C2P and newer players need to cultivate their rosters to be able to handle her. Plus EnP started releasing counters such as Kage, Seshat and Proteus. After a year plus focusing on Guin tanks, many had a “go to” raid team that could reliably handle Guin.
When other strong tanks began showing up in the top 100 raids, players were reluctant to shift tactics and SGG chose not to release counters (including 4* costumes tailored for that strong green tank).
Guin tanked most top 20 until Telluria though some had gone purple (Kunch first then Urs). Saw red tanks with BK for a spell. Then purple tanks with Bera flanked by Frigg and Odin.
The halcyon days of EnP were with the queen in the middle. But that is in the past. You guin some you lose some.
I’m still a bit weak in the yellow department, so I’m going to keep and level her. Invaluable input; cheers mate 
).
