Tanny being an Illusion Mesmer and bringing hexes sounds good to me. Being backed up by a Necromancer with hexes also sounds good. Then, we could have an air elementalist with spike skills. We'd also need a monk. A Boon Prot seems to be effective. Although the monk will be under constant pressure.
The elementalist could bring Glyph of Lesser Energy and Heal Party to aid the monk with the healing. With this line up, we'd have four casters, with us all being vulnerable due to our low armour levels. Of course, if we overwhelm the opposition with hexes, it should be expected that they are countered with something like Healing Breeze or hex removers. So, maybe if the mesmer brings an enchantment removal skill, as well as the Necromancer, Healing Breeze could be removed. It should also be expected that they cover healing breeze with another enchantment, which is why we could use two or three enchantment removal skills.
If the opposing team has a warrior, it is probably expected that it will harass the monk. So maybe if the elementalist could bring Blinding Flash, it could help. Then a Necromancer hex, such as prince of failure will further increase the warriors chance to miss, meaning that stacked with blinding flash, it is going to miss almost every time. Prince of failure will also deal 6...25 damage everytime the foe misses. So, it would be pretty painful for the warrior. We just have to hope that Blinding flash and Prince of Failure don't get removed.
I haven't even started talking about the Mesmers on the opposing team...they would be a big pain to us, as we'd all be casters if we went through with this build.
And a final point. Almost every team will have an elementalist with Searing Flames. It's a new skill which needs to be nerfed quick

. It's being misused, because it has a low recharge time of two seconds, and can cause burning for 6 seconds! Also, used with Glowing Gaze, you can get your energy back very quickly. So, Mantra of Flame could be useful here.

Anyway, I thought I'd just post the random things that came into my head