Really good heroes, but this team wouldn't scare me - Guin is just okay as a flank. If you had Alberich, I've seen her be quite effective between the tank and Alberich (basically keeping him alive to resurrect the rest of the team) but otherwise to me a lot of her mana cut mojo gets lost when she goes off less often.

Magni is a lot better in flank, where his defense up goes on the tank too. I would flip him and Guinevere (especially since he turns into a one-shot sniper with Kunchen's defense down, whereas she doesn't do any damage), and put a real green damage dealer on the far left instead of Guin - Evelyn, Liana, Gregorian, even Tarlak would work.

I personally wouldn't play Kunchen at flank - he's too slow. But I see it a lot, so maybe that would work for you, put Guin at tank, and flop Onatel out for the green damage dealers above.

This defense probably holds about 2500 overnight or so....I think if you make those changes you can get up to around 2600.

Tl;dr - it's great that you have Guin and Kunchen - but you'll probably be better served with one or the other - they are both best at tank and only 'pretty good' at other spots.