You can solo everything up to and including challenging with any gearset. lol just depends on playstyle which way you want to do it. Where D3 really shines is the 6pc classified and the legendary missions, they are soloable, including the new ones with this set due to the benefits it gives.
@Radeon85 regularly does it still.
I always found tacticians a boring gearset for solo PVE to be honest, chucking skills and cowering behind cover so I want for something to utilise gunplay.
4pc strikers is still a super strong set if you don't have 6 piece classified, and if you have a ninjabike backpack you can basically make a HoK striker build with haste from tacticians which is crazy. 3 piece striker, 1 piece nomad, 1 piece tactician, ninjabike.
but then...depends on playstyle
@SiDeards73 there are a few who still play on discord but not many.