Oh. Certainly.
So mercenary is a melee powerhouse with aoe cc+party temp hp and damage reduction. He basically works as a battery for the team and has amazing sustain in melee. Most weapons work but recommended ones are the executioner sword and halberd. For ranged go with your own personal preference. I like the handgun to snipe specials from afar.
Witch Hunter Captain is almost the same as mercenary. He has great melee sustain with a aoe cc that adds crit for increased team dps. He also works as a buffer/debuffer with his triggers like marking enemies for benefits and increased dmg. With a WHC in the team. Nobody needs to use shrapnel on their trinkets besides maybe the WHC himself to maximize dmg increase vs patrols. (Like tossing a fire grenade to debuff them). As for weapons I prefer the duals and brace pistols. But I’m certain whatever you’re most comfortable with works too.
Shade is the murderer of the team. While Merc and WHC can pretty much handle themselves very well they do an even better job together in sync. Add a Shade in the mix and you have a heavy hitter that can fight with ease with the Mercs and WHC support. Not to mention the fact that Shade can pick off key targets like chaos warriors or bannermen with ease. Also works on specials. Not to mention how quickly a shade kills a monster boss with the assistance of a WHC debuffs/buffs. Dual daggers and short bow. All the way 
Ironbreaker is the most important class in any team. Especially since the IB with correct setup and talents literally carries the entire team. An IB with dual maces, barkskin necklace and the talent that reduces taunt cool down is just to OP. You can pretty much taunt every single time. Horde coming at you? Go right in and taunt. Patrol? Taunt. You get the taunt back so fast you can use it at every encounter.
Oh and ofc during taunt the IB takes 50% less dmg. Combine that with his default 30% reduction and an additional 40% from barkskin. Yeah, you never have to block. You just hit back and win. So with a good IB the rest of the team hardly gets hit at all during larger encounters like hordes or patrols.