Interesting skills to base duo+ builds around

So, what are some interesting skills that can be used to create some duo+ builds in your opinion. I'm constantly looking for fun builds to create but with so many skills in the game, I'm sure there are plenty of skills I overlooked.

This isn't meant to be a discussion of what powerful 7 hero builds to use. Rather, I was hoping that players could talk about interesting and overlooked "skills" that have no real effect on its own, but are meant to be used in conjunction with other elements of the game to create fun and creative builds. This way, when somebody runs out of ideas for fun builds, they can come here and maybe realize there was an interesting skill they forgot about.

Here are some that I'm looking at now:

Fragility
I'm having fun with this in a duo build with a Dervish. Along with some AOE conditions and Reap Impurities, it's pretty fun and kills things fairly fast. Fevered Dream works well with this.

Frustration
Combined with additional interrupts from the party, such as Panic or dazed condition, it's very fun. Heroes don't seem to use this on martial enemies so it's best used by the player, combined with skills that can interrupt martial attacks (Clumsiness, Wandering Eye, etc.)

Warmonger's Weapon/Wailing Weapon
You can use fast attacking Assassin for constant single target interrupts. Or you can take some AOE attackers for a more party wide effect. Doesn't lead to more damage but fun to take as an extra on a Channeling Rit. Combine this with Frustration for some damage and more fun.

I'm not sure if Discord or physical damage boosts are worth mentioning since I see people talk about these skills quite often so I'm sure nobody overlooked these skills.

Lately I have been using Anton as a critical barrager for FoW, iirc my necro is carrying Warmonger's Weapon. Does wonders while facing the skeletal foes and I simply spam WS around with my dervish to finish them quickly.

Of course I usually have either Warmonger's Weapon or Splinter Weapon cast on me.

I'm not very skilled at build creation, the only other combo I can think of is Earthbind + Earthshaker.

Ritualist spamming GDW on a Scythe team

For example,
[email protected] for +20dmg, Knockdown chance 40% for virtually a guaranteed KD on balled up foes each attack, Ebon Battle Standard of [email protected] for additional +15dmg/hit, Rending Aura for easy stripping of enchantments on KD foes. Earthbind for 3 second KDs, also allowing you to KD foes normally immune to KDs. Low [email protected] for armor ignoring 120dmg on KD foes + Cracked Armor. With the easy application of Cracked Armor, Reap Impurities will be extra fun. Probably best with an AE snare and a good way to ball up foes.
Can continue to build from there with skills that benefit from KDs, conjures, and adrenaline boosts.

Alternative is a GDW Rt + Conjure Barrage rangers.