The main reason enmity combos were not liked and used as little a possible is because they done less damage, not only in the form of lower potency, but also in resource generation. This is why, the standard start to a fight was enmity combo in tank stance, then swap to DPS stance for the remainder of the fight (this is mainly coming from a SB point of view).
First, 'more potency' on finishers doesn't help as I imagine you are trying to balance the damage loss from the resource with extra potency in the combo ender, which doesn't work due to a variety of reasons, but mainly the 2 minute meta (like it or not). However, for the individual jobs:
Paladin, losing the flexibility afforded by Divine Might for when you have to disconnect is a massive loss and whilst Holy Spirit can still be used, it isn't as flexible as you have to stand still and it is weaker.
Warrior, Reducing gauge generation for less Flee Cleave goes against the very fibre of Warriors and the healing isn't significant enough to warrant using it for that purpose either.
Dark Knight, same as Warrior, just for Bloodspiller, however it is even more egregious as they only have 1 combo as opposed to Warrior's 2.
Gunbreaker, First, Brutal Shell is the second combo hit and doesn't generate gauge, Solid Barrel is the one you are thinking off, but that doesn't produce a shield/heal. Also, having less cartridges to spend means less Burst Strikes, which, considering the recent changes to Gunbreaker made sure that the amount of cartridges you generated over a 2 minute window didn't change, is counterintuitive to that.
Noone wants less of the fun stuff.
Now, if we imagine this system works and you have to balance an enmity generator and a damage combo, we need a way to properly track this all so we can make proper judgement calls. Valance has said that there needs to be an improved UI, but how would this be done? What challenges ned to be considered?
First, we have to remember that enmity is a variable that gets larger and larger as a fight goes on. If we have a meter that tracks it, the whole meter is the top enmity and there is a bar that moves based on second in the enmity list, this is as basic as you can get. Now, to throw out some numbers. If this gauge is 100 units long, at the start of the fight, you have 100 enmity and the person behind you has 90. It is easy to see they are behind you, but the numbers are close enough that there is still a lot of volatility in the values. If we look later into the fight, max enmity is 1000, if everything has scaled up evenly, the second would have 900 enmity but the bar will be less volatile. But we are using this to get as many damage combos in as possible, so the second place will be closer, call it 950. Assuming the enmity bar is linear, this value will be closer to max than the initial example, so, do you have the room to do another damage combo?
How about if we use more realistic enmity values where they get closer to 100,000+ At 100,000 enmity, the second place could be at 99,000, which could be plenty of leeway for a damage combo, but, because of the resolution of the bar, 99,999 could also be 1 unit shy from filling, where you do not have that luxury and need to use the enmity combo. The point here is his gets less and less reliable so you are more likely to fall into a rhythm of x damage combos per enmity combo just to ensure you stay ahead, at which point, you aren't managing enmity, just following a rotation.
This is the first thing that has to be sorted out first if any sort of proper enmity management is to be implemented. There are other concerns I would have after that, but they do not matter unless a coherent Ui element can be put into place.
