Theorycraft
Talent Calculator for Hunter, Titan and Warlock - Destiny Database (DestinyDB)
In an ideal raid group why bring a Hunter?
2-3 Titan with Defender Subclass
1st Titan = WoD (Blessing of light)
2nd Titan = WoD (Weapons of Light)
3rd Optional Titan = WoD (Armor of Light)
3x Warlock a mix of Voidwalker for damage and Sunslinger for Damage/Support
2x Sunslinger with Radiance (Song of Flame) = Reduces all cooldowns for nearby allies.
If you need Arc damage one of the Titans can spec Striker build. And who would you want in melee in a boss fight? A Titan with Striker spec or a hunter with Bladedancer spec? Titan also gets Flashbang.
I am not trying to knock on a Hunter by why bring one at all? If you need more defense your Titans can switch subclass for a more team oriented defensive spec that benefits everyone. If you need more offense they can spec into direct damage or group abilities that increase damage. The Warlocks can go full offense with Void walker or group offense with Sunslinger and Radiance cooldown reduction so Titan's can constantly use weapons of light on everyone.
Now on the other side of the argument, if the Hunter's single target damage is exceptionally superior to the others then it may turn out that the ideal group is 1x guardian 1x Sunslinger (cooldown reduction) and all the rest hunters. We have seen this scenario happen often enough in MMO's