Ranged DPS ground target AOE stacking

[R1CH]

Currently several classes (mainly BW, Sorc, Engi, Magus) have ground targeted AOE spells that do not stack, either the first caster gets priority or the person with the most skill points gets priority. When your cast is overwritten by another in the same area, it feels bad as you're spending a cooldown and GCD on nothing. It also often happens that a player with high level gear (and thus more damage) will have their cast overwritten by someone with lower gear but more points in the tree. This problem is especially bad on Engi and Magus where their core damage abilities in AOE spec have longer cooldowns compared to other classes.

Rather than the simple first caster / most skill points taking priority, I'd propose that for each damage tick on each player, the game rolls the damage value for every stack in the same area and picks the one that does the highest damage, including accounting for dodge/disrupt and crits.

As an example, say there are three engineers casting Phosphorous Shells in the same area. For each enemy player in the AOE, the following would happen:

Tick 1:
Engi 1 rolls for 200 dmg
Engi 2 rolls crit for 400 dmg
Engi 3 gets dodged
Final damage this tick: 400 dmg credited to Engi 2

Tick 2:
Engi 1 gets dodged
Engi 2 rolls for 180 dmg
Engi 3 rolls for 220 dmg
Final damage this tick: 220 dmg credited to Engi 3

and so on. With the random chances of dodge/disrupt and crit, this means that there's a chance each person casting in the same area will hopefully get at least a few ticks of damage out of their cast rather than it being completely wasted, while at the same time increasing the overall damage of multiple casts and naturally capping the total damage to no more than if every tick was a critical hit.