The last area brought many new mercs and some of them were quite impactful on PvE, now we have builds like bainegore and pirates which are viable but there are many possibilities not yet explored.
I’ll be honest, I’m not taking pvp in consideration.
Healin Trio
With the addition of baine, we just need a green merc with healing power boosting to combo him and chi ji in order to create a healing comp, that can be useful against bosses that need to be beaten slowly like balinda, and if the merc is rare it can be also a cheap opportunity to f2p players as baine is already rare.
Shadow
I think this comp has 2 main problems:
1- It still dont have a solid booster like brukan does with nature.
2- Its 2 main chars are both blue (Voljin+Azshara), so u are in a disadvantage vs fighter mercs
Maybe if one of them was red this could be a more solid comp as we already have good green mercs who can do shadow damage (Just remembering that I have no idea on how this could impact on pvp).
Dont get me wrong, I farmed some bosses with shadow already but its still too weak in comparison to builds like nature or frost.
Arcane
I think this build mechanics are based in 2 types:
Heavy single target damage is possible as Tyrande has good green damage just as azshara and blink fox, we just need a red merc to support this.
For a faster approach, We need to give millhouse the new buffs treatment, by absorbing his damage boosting equip into his 1st skill so we can actually choose between other equips.
Also If a red arcane merc comes, he could have a passive equip to boost arcane damage (just as rag does in the fire comp) and a multi target arcane 0 recharge attack with low-medium damage (doesnt needs to be an full aoe as millhouse already has one), maybe with some conditioning to boost his damage like Tyrande does with her 1st equip.
So I think the arcane team gimmick can either be slow with heavy damage or multi-target based.
Neutral mercs
Its about time we have a neutral merc, I dont know if this could be a nice balanced thing as it will not be able to take neither perform critical damage.
Maybe a merc that can swap roles with a skill and change the rest of his skillset depending of this choice so we can insert it in multiple comps.