its my understanding that the inefficiency lies within the timer expiration (such that, the more times the timer expires, the less efficient) - this is completely non-dependant on the number of timers
however - if you have 1 spell with a timer stack, and 1 spell with a timer per instance, each running 5 at a time, sthe first spell will be more efficient because there are less timer expirations, now because there are less timers
as for Cohadars theory (unproven?) I didn't really see you benchmark that, aside from the last test which only mentioned KT1 and KT2 (aside from "After 4-5 different spells, the number of spells becomes completely irrelevant to these systems. " - which made no sense to me)
lets consider an AoS for a second, max of 12 players
assume 1 hero/player, 5 spells/hero - if we were to assume that at any given time, 25% of these heroes could have 2 spells active with effects - that would give is 12*.25*2 = 6
granted each spell could require more then one timer for its effects (if done on the timer/instance basis) - but lets assume that is not the case
therefore, at any given time there are 6 spell instances active - most often then not ppl do not allow multiple of heroes, thus a timer stack would be uneeded (since only 1 instance would ever be active - unless for some goofy reason the effects last longer then the spell cd)
I think its safe to assume that, unless you know your map is using mutiples of heroes, or there is the possibility for 3+ instances of your spells at a given time, the easiest way, and most efficient, is just generic timer attachment
however - if you have 1 spell with a timer stack, and 1 spell with a timer per instance, each running 5 at a time, sthe first spell will be more efficient because there are less timer expirations, now because there are less timers
as for Cohadars theory (unproven?) I didn't really see you benchmark that, aside from the last test which only mentioned KT1 and KT2 (aside from "After 4-5 different spells, the number of spells becomes completely irrelevant to these systems. " - which made no sense to me)
lets consider an AoS for a second, max of 12 players
assume 1 hero/player, 5 spells/hero - if we were to assume that at any given time, 25% of these heroes could have 2 spells active with effects - that would give is 12*.25*2 = 6
granted each spell could require more then one timer for its effects (if done on the timer/instance basis) - but lets assume that is not the case
therefore, at any given time there are 6 spell instances active - most often then not ppl do not allow multiple of heroes, thus a timer stack would be uneeded (since only 1 instance would ever be active - unless for some goofy reason the effects last longer then the spell cd)
I think its safe to assume that, unless you know your map is using mutiples of heroes, or there is the possibility for 3+ instances of your spells at a given time, the easiest way, and most efficient, is just generic timer attachment