For PLDs they could bring back War Drum to give them an AoE when you block you send shockwaves in a cone in front of you for X Potency would work well with Bulwark and Sheltron or even adding a burning DoT on flash (20 potency stacks 3 times for 60 potency).

For Drks they have amazing AoE (Unleash, Abyssal Drain, Dark Passenger, Salted Earth) but as stated they don't have a physical one which would be nice like a line attack (much like Praetorium Gaius X shaped slash) would be interesting.

Wars could just add a cleave in Butchers Block to keep it's synergy going or when using Steel Cyclone/Decimate it leaves a tornado eventually sucking things in and doing wind damage. I don't really know how to "improve" wars when their toolkit is the best in the game so any ideas would be great.