Polymorpher: sounds like there can be a lot of utility and diversity in this skillgroup. Hiding as a pet, flying onto new areas, breathing under water. Hence my favourite (and I want to be a manticore! because its overpowered).
Trap Master: There is some shenanigans possible like smoke grenades and immobility traps amidst a city (and no one knows who placed them...). Unfortunately, traps work best if you know your environment well. Now that discovery is an important part of the game whatever I can imagine works in special scenarios only (you are about to activate the alarm in a heist, assassinations of people you already know,...). It will at least take a lot of time to pull off.
Bard: Bards are nice at the way dialogues work in D:OS. Combat-wise they need to be strong against single enemies (bosses ofc) and when competetive questing occurs. You can work around that.
Unarmed Combat: I cannot imagine what it offers over other fighting skills. Might be quite innovative. And it might be boring as well. I have no idea.
Summoning master: Summons have been really strong. Moreso since APs are being reduced. Also it sounds like it will have little interactions with other skills. It all depends on what those summons will do (which might be anything).
Juggernaut: The idea of a low-health-high-reward warrior might have a lot of synergy with other skilltrees, because you need to keep those characters alive. You can heal them, juggle with them strategically so they do not get hit, you might give those same characters protective skills as well and you need to make sure there is as little harm from area effects as possible.
Guardian: Tanking has its own limits already set in stone. So if it is possible to play the game without them, these skills are in heavy danger of being irrelevant, unless they can do a lot that is not tanking, but crowd control and magic(al shielding). They might work if you can avoid movement or mitigiate insta-death effects in boss battles. But then again, they are still (not 100%) feats of convenience.
IDEA: Guardians can active/passively block arrows directed at others and enemy movement.
Alchemist: Alchemists can be considered extremely diverse, even including nearly every skill that might be included into the Trap Master set. The only tragedy might be when Both Trap Master and Alchemist get the most votes. Just because of its limitless possibilities this one is my other favorite.
