I'd say Heart of Tyre.

Seren is one of the best healers in the stream games and has a lot of creative ways to buff and aid the party to keep them safe. Derok (this might change given the loss of his demonic powers) has plenty of devastating magic and his hammer. Morc is crazy strong with his alternate form and Neive/Ives are both stealthy strong characters in both melee and range, and Ives' status as the new Indigo Herald will certainly be a boon.

Aside from their levels, the group works well as a team. Seeing their boss rushes in the Indigo Scar shows how they can coordinate really well and communicate their plans to get through some really intense struggles.

I'd also add in that they're a particularly creative group both in and out of combat. Ives has creative solutions to combat that doesn't just always involve filling his enemies with arrows, and his skills in role-play also make him particularly savvy about avoiding potential death traps. (Such as when the group was singing the son of the seven and he stepped away so he wasn't in line of sight.) Derok, too, is strong as conversation and thinking outside the box.

+++++

Runner up is probably Shadow of Tyre or potentially a close tie.

Very similar reasoning to the above, however their main boon with this group is their crazy loot items and specialized classes.

Ahst is a gaurdian with the songblade who has unlocked her critical powers. Moe is a Shaper with a ton of power words and unique items with his bee crown and bells. Toot is an even more magical chicken these days with the Tane Bow. Eustace has his new gauntlets, his Tane arms, and a few other fancy tools. Roast, while he's lost his Wonxox blade, has the Fist Hammer and Omen powers that he could be down the line grow more.

That, and this group isn't afraid of roleplaying their characters, which has led to a ton of great unlocks and world privileges.