Battle Regimens had the promise of encouraging balanced parties, because of the requirement to use weaponskills from different classes in order to get damage boost (weaponskills from same classes simply removed cross-class affinity penalties).

However, the clunkiness of the battle regimens, together with the still-high affinity of cross-class skills has rendered Battle Regimens less useful then they could have been.

However a system like this, that rewards diversity, without REQUIRING particular classes is the best of both worlds. You don't need any particular class to increase overall damage, but you can't bring 8 of the same class, or your BR will be weak.

Another example, already mentioned, is to give enemies skills that can be used reactively. For example, an enemy could have slashing, piercing, projectile, magic, and elemental defense buffs, but only ONE can be active at a time. The enemy uses the buff corresponding to the biggest damage source. Another way to encourage party diversity.

One thing I DON'T want to see is a simply reversal of the situation, where melee is king, lolARC becomes a byword, with CON and THM relegated to basic healbots. I've seen this situation in other MMOs as well, and it's just as ugly as OPed ARC / THM / CON.